Improved sanitizing of configuration names which have a number prefix.
[Resolver] Don't include `nil` results.

Fixes #2733.
[ResolverSpec] Add a test case for subspec dependencies where not all versions have a subspec with the given name
Drop support for Ruby 1.8.7
Merge pull request #2718 from CocoaPods/ruby2

Drop support for Ruby 1.8.7
[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`
Drop support for Ruby < 2.0.0
[bundle] update
[profile] Add KCacheGrind profile printer with `.callgrind` extname.
[Travis] Run on all Ruby versions that come with 10.9 and 10.10.
Merge remote-tracking branch 'origin/master' into number_prefix_preprocessor_definitions
Improved sanitizing of configuration names which have a number prefix.