Merge branch 'arthur/update-travis-config'

Author: arthurschreiber

.travis.yml

@@ -11,15 +11,15 @@ os:
 rvm:
   - 1.9.3
   - 2.0.0
-  - 2.1.2
+  - 2.1.5
+  - 2.2.1
   - ruby-head
   - rbx-2
 
 matrix:
   fast_finish: true
   allow_failures:
     - rvm: rbx-2
-    - { os: osx, rvm: 2.1.2 }
 
 install:
   - ./vendor/libgit2/script/install-deps-${TRAVIS_OS_NAME}.sh