Migrate a Formula to Multiple Versions: add docs.

cleanup: remove GLIDE_HOME cache directories

This is needed since some formulae now set

  ENV["GLIDE_HOME"] = HOMEBREW_CACHE/"glide_home/#{name}"

brew.sh: improve user agent with no git repo.

Rename FormulaMethodDeprecatedError to  MethodDeprecatedError.

Remove Homebrew Cask documentation.

Make parsing locales more robust.

`Homebrew/>1.0.0 (no git repository) (Macintosh; Intel macOS 10.7.5)...)
reads pretty weirdly in a user agent and I've had complaints that `>`
may be an invalid character in some cases.

audit: forbid `deprecated_option` in new formulae

Deprecate license

Make `core_tap_version_string` reusable.

* Fix IntegrationCommandTestCask

“Homebrew Cask” -> “Homebrew-Cask”

Fix exit code for multilingual cask audit.

Change `A Cask for #{token} is already installed.` message.

Add `.com.apple.timemachine.supported` to DMG_METADATA_FILES.

virtualenvs remember the prefix of the python that created them and do
magic to load packages from them; help them remember a more durable
path.

Refactor Cask’s extensions.

Use `module_function` for `Homebrew` module.

brew.sh: don't autoupdate if --help passed

fix tests failing when verbose set

Formula-Cookbook: fix /usr/local/Homebrew references.

virtualenv_install_with_resources: select correct python

Make `MacOS.language` less opinionated and add `language` stanza.

`virtualenv_install_with_resources` will now attempt to guess the
desired Python based on the active build options and based on the
dependencies and requirements. When the situation is ambiguous (e.g.,
`depends_on :python3` and `build.with? "python"` is true) raise
`FormulaAmbiguousPythonError` unless `:using => "python"` or
`:using => "python3"` has been passed to resolve the ambiguity.

In most cases, this will allow

```
    virtualenv_create(libexec, "python3")
    virtualenv_install_with_resources
```

to be changed to just

```
    virtualenv_install_with_resources
```