Revert "Revert "Merge pull request #10 from sanemat/feature/travis-use-2-1-0""

This reverts commit dcbba334c8b686ac1d61b17eae109cfabd679349.
Use bundler 1.5.1
Merge pull request #11 from sanemat/fix/re-re-2-1-0

Revert "Revert "Merge pull request #10 from sanemat/feature/travis-use-2......-1-0""