Update CocoaPods version class to support prerelease version strings that conform to the Semantic Versioning specification. fixes CocoaPods/Core#4
Merge branch 'bugfix/4-conform-to-semantic-versioning-spec' of git://github.com/blakewatters/Core into blakewatters-bugfix/4-conform-to-semantic-versioning-spec
Move SemVer prerelease changes to our vendor subclass.

This is so we can easily update the vendored code from upstream and to
not mangle copyright owners.