Test against Ruby 2.1.0

Closes #713.

.travis.yml

@@ -8,13 +8,16 @@ rvm:
   - 1.9.2
   - 1.9.3
   - 2.0.0
+  - 2.1.0
   - jruby-18mode
   - jruby-19mode
   - jruby-20mode
   - jruby-21mode
   - jruby-head
   - rbx
+  - ruby-head
 matrix:
   allow_failures:
     - rvm: jruby-head
+    - rvm: ruby-head
   fast_finish: true

README.md

@@ -144,7 +144,7 @@ your first stop if you are wondering about a more in-depth look at
 OmniAuth, how it works, and how to use it.
 
 ## Supported Ruby Versions
-OmniAuth is tested under 1.8.7, 1.9.2, 1.9.3, 2.0.0, JRuby, and Rubinius.
+OmniAuth is tested under 1.8.7, 1.9.2, 1.9.3, 2.0.0, 2.1.0, JRuby, and Rubinius.
 
 ## Versioning
 This library aims to adhere to [Semantic Versioning 2.0.0][semver]. Violations