Add CocoaPods file type detection

CocoaPods is to Objective-C what RubyGems and Bundler are to Ruby. It,
too, uses Ruby as the language for its dependency declaration (Podfile)
and package specification (*.podspec) files. Treat these as Ruby files.
Fix highlighting of regexps as hash keys.
Merge pull request #194 from bk2204/highlight-regex-in-hash-key

Fix highlighting of regexps as hash keys.
Add syntax highlighting for Module#refine and Module#using
Merge pull request #196 from rbright/master

Add syntax highlighting for Module#refine and Module#using
Apply real fix for Andy Wokula's HTML indent
Remove Gem installation infrastructure

This project hasn't been distributed as a gem in the better part of a decade
and the resulting user complaints have registered as little more than a murmur.

Relevant FAQ content will be moved to the wiki.

Fixes #198.
Merge pull request #192 from jvirtanen/features/cocoapods

Add CocoaPods file type detection