Better seeds.rb, newer angular version, less annoying mongoid JSON, updates to guides form.

# What's new?

 * Added rubocop gem
 * Upgraded to edge angular and pulled it from CDN instead of asset pipeline (we need ng-debounce, which is edge)
 * Continued the typeahead that @simonv3 started. Uses the new `api/crops` endpoint. Still need to handle submission.
 * Changed crops controller to return `[]` if search query is empty or < 3 letters.
 * Got rid of that wacky `{"_id" : {"$oid": "123"}}` mongoid OID serialization.
 * Improved `crops_factory` for better testing
 * Wrote a better `seeds.rb` (pun alert) and updated the README with usage instructions.