class XSemVer::SemVer

def prerelease=(pre)

TODO: Deprecate #special= in favor of #prerelease=?
To be consistent with the specification verbage, #prerelease= sets the same value as #special.
SemVer specification 2.0.0-rc2 states that anything after the '-' character is prerelease data. 
def prerelease=(pre)
  self.special = pre
end