Drop support for Ruby < 2.0.0
Merge pull request #212 from CocoaPods/ruby2

Drop support for Ruby < 2.0.0
Drop ISAS_SUPER_CLASSES because we have now ordered hashes
Remove version condition from spec
Merge pull request #213 from mrackwitz/ruby2

[Ruby2] Further cleanup
Release 0.20.0
[gemspec] Allow ActiveSupport 4 usage as well.
[bundle] update
[bundle] Add rake back to make Travis green again.
[Project] Add a `shallow_eql?` method which performs a cheap comparison.
[NativeTarget] Make adding a target dependency O(1).

This greatly reduces the amount of time taken for large Podfiles.
Various doc and message fixes.
[Project] Make `#==` the fast shallow comparison method.

Because it's too hard to ensure that nobody will introduce changes into
Xcodeproj that will greatly slow down the project again.

For full data comparisons, use `#eql?` instead.
[rubocop] Disable max class length, it doesn't help.
[Object] Cache an object's plist name, which is used often.
[CHANGELOG] Document optimisations.
Merge pull request #216 from CocoaPods/optimisations

Optimisations
[Travis] Run on all Ruby versions that come with 10.9 and 10.10.
[CoreFoundation] Hopefully fix a Ruby constant lookup issue.

A few people have reported an issue where the CFAutoRelease constant
could not be found from the singleton method.

* https://github.com/CocoaPods/CocoaPods/issues/2632
* https://github.com/CocoaPods/CocoaPods/issues/2739

I have been unable to reproduce this, but because the issue has been
reported by more than one person, I'm adding this just to be sure.
Bump to 0.20.1