Test against 2.0.0 and rubinius on travis-ci
Remove test against "ruby-head" in travis-ci

travis' "ruby-head" is not ruby-head, it is too old.
"ruby-head" is ruby2.0.0dev today. This is before 2.0.0-p0
Use rbx instead of rbx-19mode
Remove test against rbx in travis temporary
Merge pull request #22 from sanemat/feature/travis-update

Update travis-ci config