Add Ruby idioms' Goals in CONTRIBUTING.md.

Author: JuanitoFatas

CONTRIBUTING.md

@@ -4,4 +4,8 @@ If you find any typos, errors, or have an better example. Just raise a new issue
 
 <3
 
+These idioms list here are trying to satisfiy following goals:
+
+[![GOALS](/images/Goals.png)](https://speakerdeck.com/sferik/writing-fast-ruby?slide=11)
+
 [JuanitoFatas](https://twitter.com/juanitofatas)