Add section on Supported Rubies

.travis.yml

@@ -1,6 +1,6 @@
 rvm:
   - 1.8.7
   - 1.9.2
-  - rbx
+  - jruby
   - ree
   - ruby-head

README.md

@@ -141,6 +141,31 @@ OmniAuth Core
 * **Michael Bleigh** ([mbleigh](https://github.com/mbleigh))
 * **Erik Michaels-Ober** ([sferik](https://github.com/sferik))
 
+Supported Rubies
+----------------
+This library aims to support and is [tested
+against](http://travis-ci.org/intridea/omniauth) the following Ruby
+implementations:
+
+* Ruby 1.8.7
+* Ruby 1.9.2
+* Ruby Enterprise Edition 1.8.7
+* JRuby 1.6
+
+If something doesn't work on one of these interpreters, it should be considered
+a bug.
+
+This library may inadvertently work (or seem to work) on other Ruby
+implementations, however support will only be provided for the versions listed
+above.
+
+If you would like this library to support another Ruby version, you may
+volunteer to be a maintainer. Being a maintainer entails making sure all tests
+run and pass on that implementation. When something breaks on your
+implementation, you will be personally responsible for providing patches in a
+timely fashion. If critical issues for a particular implementation exist at the
+time of a major release, support for that Ruby version may be dropped.
+
 License
 -------
 OmniAuth is licensed under the MIT License.