Create CONTRIBUTING.md

Inspired by:

https://raw.github.com/twitter/bootstrap/master/CONTRIBUTING.md
https://raw.github.com/twitter/zipkin/master/CONTRIBUTING.md
https://github.com/square/dagger/blob/master/CONTRIBUTING.md

Author: benjchristensen

CONTRIBUTING.md

@@ -0,0 +1,15 @@
+# Contributing to Hystrix
+
+If you would like to contribute code you can do so through GitHub by forking the repository and sending a pull request (on a branch other than `master` or `gh-pages`).
+
+When submitting code, please make every effort to follow existing conventions and style in order to keep the code as readable as possible.
+
+## Copyright
+
+If you are adding or modifying files you may add your own copyright line, but please ensure that the form is consistent with the existing files, and please note that a Netflix, Inc. copyright line must appear in every copyright notice. 
+
+## License
+
+By contributing your code, you agree to license your contribution under the terms of the APLv2: https://github.com/Netflix/Hystrix/blob/master/LICENSE
+
+All files are released with the Apache 2.0 license.