Fix a Ruby lexing bug where symbol-beginning colons were sometimes read as statement-delimiting colons.
Fix a Ruby lexing bug where symbol-beginning colons were sometimes read as statement-delimiting colons.

For example:

    def foo
      if :/
        return 12
      end
    end

Signed-off-by: Loren Segal <be97ac84963a82296fd1ab1af6358dfaa6463b0a@soen.ca>
travis-repos/yard,thomthom/yard,ohai/yard,jreinert/yard,travis-repos/yard,jreinert/yard,jreinert/yard,alexdowad/yard,ohai/yard,iankronquist/yard,alexdowad/yard,thomthom/yard,amclain/yard,amclain/yard,herosky/yard,amclain/yard,lsegal/yard,iankronquist/yard,ohai/yard,herosky/yard,herosky/yard,lsegal/yard,lsegal/yard,alexdowad/yard,iankronquist/yard,thomthom/yard