Documentation Updates

Shouldn't be anything too controversial here, but:

Acceptable-Formulae:

* Makes the language around stable versions stricter.
* Fixes the Homebrew/Head-only lack-of-hyphen.
* Adds Homebrew/Devel-only.

Formula-Cookbook:
* Adds a link to Interesting-Taps-&-Branches.
* Fixes the Python language to match Tim’s latest guidelines.
* Adds a note on options that aren’t ` build-with? ` or ` build-without? `.

Interesting-Taps-&-Branches:
* Slightly modifies the Versions language to better match what the repository actually ships.
* Adds Homebrew/Devel-only to the language.