Simple form hacks

 - [x] Globally adds class to collection inputs as requested by @demwunz
 - [x] Moves shared examples into own files from Rails helper
 - [x] Delegates Form#column_for_attribute to target object, allowing,
    SimpleForm to reason about column types and infer correct input types
 - [ ] API to add data-attributes for progressive reveal
 - [ ] "Secondary hints"