adding media selector pattern

New media selector pattern and javascript module for forms

![image](https://cloud.githubusercontent.com/assets/1566749/4081249/f61c3630-2ee5-11e4-9f4a-b95fa654d42b.png)

Only note is that when using a class as `-class-name`, the hyphen before the class name should mean that it's a modifier class (like `-odd` or `-even`, etc). The pattern name should be a non-hyphenated class name. Not a huge deal, but maybe something to refactor in the future...?