Update contributing.md

Author: bootstraponline

contributing.md

@@ -21,3 +21,12 @@ Android tests require running on physical hardware with Android 5.0 (API 21). Th
 
 - `cd android_tests`
 - `flake 3 android` - Run all the Android tests up to 3 times
+
+### Publishing
+
+0. Ensure you have `~/.gem/credentials` If not run [the following command](http://guides.rubygems.org/make-your-own-gem/) (replace username with your rubygems user)
+> $ curl -u username https://rubygems.org/api/v1/api_key.yaml >
+~/.gem/credentials; chmod 0600 ~/.gem/credentials
+
+1. Bump the version number `rake bump`
+2. Publish with `rake release`