Merge pull request #3709 from activeadmin/travistest

fix travis allow_failures
fix typo in columns.rb
test against Ruby 2.2

& don't needlessly specify the tiny version number
allow failures for 2.2 and keep testing on 2.1 until 2.2 tests are passing
Merge pull request #3714 from activeadmin/testtravis

allow failures for 2.2 and keep testing on 2.1 until 2.2 tests are passing
add `fast_finish: true` to travis.yml
change travis matrix
added rtl support