Updated travis build scripts (from rspec-dev)
see if we still need rbx specific dependencies
Merge pull request #1463 from rspec/update-travis-build-scripts-2014-03-29-for-master

Updates from rspec-dev (2014-03-29)
Merge pull request #1464 from rspec/try_travis_without_rubysl

Try Travis RBX builds without specific gemfile dependencies
Provide assertions accessor for minitest.