Allow failures on AR edge
Try rbx-2 on travis

According to https://github.com/travis-ci/travis-ci/issues/2230#issuecomment-42742477, we should use rbx-2 for now.
fix a bug where :view_paths wouldn't be inherited to nested helpers. added a stronger test.
Merge pull request #553 from apotonick/views-prefix

Fix a bug where :view_paths wouldn't be inherited to nested helpers.
Fix wrong travis config
Use padrino helpers ~> 0.11.0 if Ruby version is 1.8.7
Try using minitest on rbx instead of rubysl-test-unit