Update a note on required versions of Ruby
Stop running tests with MRI 1.9.3 on Travis CI
Run tests also with MRI 2.1.0 on Travis CI
Add PlainVersion, as a copy of Version
Change Version as a proxy of PlainVersion
Add BranchVersion
Support BranchVersion in Version.create
Refine VersionConstraint specs a bit
Add missing specs on VersionConstraint.parse
Ignore trailing spaces in a version constraint
Support BranchVersion in VersionConstraint
Refine a spec on LockFile#flavors
Refactor LockFileParser on plain_version
Support BranchVersion in LockFile/LockFileParser
Simplify FlavorFile#flavor with keyword arguments
Refine test descriptions on FlavorFile
Support FlavorFile#flavor with a branch option