[Gemspec] Update molinillo dependency to `~> 0.1.0`
[Gemfile] Remove libxml2

This has no longer been a dependency of Xcodeproj
Move master repo checks to its own method
Ensure master repo setup in search
Update changelog
Merge pull request #2719 from CocoaPods/libxml2

[Gemfile] Remove libxml2
[CHANGELOG] Clean up entry from #2563
[Command] Remove unnecessary `.parse` implementation
[Gemspec] Update Xcodeproj dependency to `~> 0.20.0`