Remove Achievables

* Creates migration to drop achievables and achievables tables
* Updates db schema
Remove Achievables

* Deletes all related with achievables
* Deletes relationship between user and achievable
Remove Achievables

* Fix specs
Revome Achievables

* Remove workshops controller
* Remove workshops views
* Remove workshops model
Merge branch 'master' into feature/remove-achievables

Conflicts:
	db/schema.rb
Merge pull request #30 from crowdint/feature/remove-achievables

Feature/remove achievables