Bumps [parallel_tests](https://github.com/grosser/parallel_tests) from 2.22.1 to 2.23.0.
- [Release notes](https://github.com/grosser/parallel_tests/releases)
- [Commits](https://github.com/grosser/parallel_tests/compare/v2.22.1...v2.23.0

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [ruby-progressbar](https://github.com/jfelchner/ruby-progressbar) from 1.9.0 to 1.10.0.
- [Release notes](https://github.com/jfelchner/ruby-progressbar/releases)
- [Changelog](https://github.com/jfelchner/ruby-progressbar/blob/master/CHANGELOG.md)
- [Commits](https://github.com/jfelchner/ruby-progressbar/compare/releases/v1.9.0...releases/v1.10.0

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [parser](https://github.com/whitequark/parser) from 2.5.1.0 to 2.5.1.2.
- [Release notes](https://github.com/whitequark/parser/releases)
- [Changelog](https://github.com/whitequark/parser/blob/master/CHANGELOG.md)
- [Commits](https://github.com/whitequark/parser/compare/v2.5.1.0...v2.5.1.2

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [rspec-expectations](https://github.com/rspec/rspec-expectations) from 3.8.0 to 3.8.1.
- [Release notes](https://github.com/rspec/rspec-expectations/releases)
- [Changelog](https://github.com/rspec/rspec-expectations/blob/master/Changelog.md)
- [Commits](https://github.com/rspec/rspec-expectations/compare/v3.8.0...v3.8.1

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [docile](https://github.com/ms-ati/docile) from 1.3.0 to 1.3.1.
- [Release notes](https://github.com/ms-ati/docile/releases)
- [Changelog](https://github.com/ms-ati/docile/blob/master/HISTORY.md)
- [Commits](https://github.com/ms-ati/docile/compare/v1.3.0...v1.3.1

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [parallel_tests](https://github.com/grosser/parallel_tests) from 2.22.0 to 2.22.1.
- [Release notes](https://github.com/grosser/parallel_tests/releases)
- [Commits](https://github.com/grosser/parallel_tests/compare/v2.22.0...v2.22.1

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [rspec](https://github.com/rspec/rspec) from 3.7.0 to 3.8.0.
- [Release notes](https://github.com/rspec/rspec/releases)
- [Commits](https://github.com/rspec/rspec/compare/v3.7.0...v3.8.0

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [parallel_tests](https://github.com/grosser/parallel_tests) from 2.21.3 to 2.22.0.
- [Release notes](https://github.com/grosser/parallel_tests/releases)
- [Commits](https://github.com/grosser/parallel_tests/compare/v2.21.3...v2.22.0

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [rubocop](https://github.com/rubocop-hq/rubocop) from 0.57.1 to 0.57.2.
- [Release notes](https://github.com/rubocop-hq/rubocop/releases)
- [Changelog](https://github.com/rubocop-hq/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop-hq/rubocop/compare/v0.57.1...v0.57.2

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [rspec-retry](https://github.com/noredink/rspec-retry) from 0.6.0 to 0.6.1.
- [Release notes](https://github.com/noredink/rspec-retry/releases)
- [Changelog](https://github.com/NoRedInk/rspec-retry/blob/master/changelog.md)
- [Commits](https://github.com/noredink/rspec-retry/compare/v0.6.0...v0.6.1

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [rspec-retry](https://github.com/noredink/rspec-retry) from 0.5.7 to 0.6.0.
- [Release notes](https://github.com/noredink/rspec-retry/releases)
- [Changelog](https://github.com/NoRedInk/rspec-retry/blob/master/changelog.md)
- [Commits](https://github.com/noredink/rspec-retry/compare/v0.5.7...v0.6.0

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [parallel_tests](https://github.com/grosser/parallel_tests) from 2.21.2 to 2.21.3.
- [Release notes](https://github.com/grosser/parallel_tests/releases)
- [Commits](https://github.com/grosser/parallel_tests/compare/v2.21.2...v2.21.3

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [simplecov](https://github.com/colszowka/simplecov) from 0.15.1 to 0.16.1.
- [Release notes](https://github.com/colszowka/simplecov/releases)
- [Changelog](https://github.com/colszowka/simplecov/blob/master/CHANGELOG.md)
- [Commits](https://github.com/colszowka/simplecov/compare/v0.15.1...v0.16.1

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

Bumps [rspec-retry](https://github.com/noredink/rspec-retry) from 0.5.6 to 0.5.7.
- [Release notes](https://github.com/noredink/rspec-retry/releases)
- [Changelog](https://github.com/NoRedInk/rspec-retry/blob/master/changelog.md)
- [Commits](https://github.com/noredink/rspec-retry/compare/v0.5.6...v0.5.7

)

Signed-off-by: dependabot[bot] <support@dependabot.com>

A bunch of these were needed before superenv, environment filtering or
on now long-unsupported versions of macOS.

We have a few tests that are intermittently flaky. Let's try this to see
if we can get them a bit more reliable.

This matches the version that supports Ruby 2.3.3 syntax (which is the
version we use).

This requires updating to Rubocop 0.49.0 which will require some fixes
to rules, in Homebrew/brew and Homebrew/homebrew-core but opening this
for now so I remember.

Attempt to improve Travis CI. This time without any vendoring gems
nonsense.

This reverts commit 3e4547f5, reversing
changes made to 6edf9382.

Homebrew's actually ended up using a fair few gems. While we want to
avoid Bundler at runtime (and this PR still does that, in fact uses
Bundler even less at runtime than it did before) writing our own version
to use at build-time seems redundant.

We’re upgrading SimpleCov to 0.13.0 so let’s update the rest of our
gems while we’re at it.

OS X Travis CI is particularly error-prone, slow and unnecessary for
us when we're already running (fast) OS X builds on Jenkins so use it
just for Linux testing.