Outputs the merged pull requests on Homebrew/brew between two Git refs.

### Is there a glossary of terms around?
All your terminology needs can be [found here](docs/Formula-Cookbook.md#homebrew-terminology). results in 404 error

Write the README but also a `.travis.yml` file (and in future perhaps a
`Jenkinsfile`).

Addressing a few spots where I looked for terminology and did not find what I was looking for. Input based on a recent [podcast with Mike](https://changelog.com/podcast/223)

Update to the latest status quo.

These are the ones that are auto-installed without tapping and it makes
sense to make them more prominent in our documentation as we've
offloaded various functionality over the years to each of them.

Add a document describing how to migrate a formula to our new multiple
versions support, upgrade a multiple version formula and how to import
a homebrew/versions formula into homebrew/core.

This option is used to test updating between tags.

As requested in #1199 this updates the documentation accordingly for
that change.

Add some missed changes. I'll add a CI check for this at a future point.

From the 8.1 Xcode Beta:
```
There is no Command Line Tools (OS X 10.11) for Xcode 8 package. Xcode 8 contains
SDKs that are incompatible with earlier toolchains. Developers who want to make
use of the Xcode 8 SDKs from the command line must choose the SDK with `xcode-select`.
Developers on OS X El Capitan who have installed versions of the Command Line Tools
(OS X 10.11) for Xcode 8 Beta should install Command Line Tools (OS X 10.11)
for Xcode 7.3.1.
```

Thanks Apple.

Closes #1040.