Workaround for Rubinius version error on Travis.

See: http://docs.travis-ci.com/user/languages/ruby/

.travis.yml

@@ -4,7 +4,7 @@ rvm:
   - 2.0.0
   - 2.1.0
   - jruby-19mode
-  - rbx
+  - rbx-2
 gemfile:
   - Gemfile
   - gemfiles/Gemfile.mongoid-2.4.x
@@ -26,6 +26,6 @@ matrix:
     - rvm: jruby-19mode
       gemfile: gemfiles/Gemfile.mongoid-2.4.x
       env: SSL_CERT_DIR=/etc/ssl/certs
-    - rvm: rbx
+    - rvm: rbx-2
       gemfile: gemfiles/Gemfile.mongoid-2.4.x
       env: SSL_CERT_DIR=/etc/ssl/certs