audit API access and writes

- refactor api_spec to use lets
- api_access audit of GET's
- api_write audit based on model before_save hook w/sweeper
Move classes and modules in lib/audit/user_action.rb to their own files
Merge branch 'devel' into feature/audit_api_access

Conflicts:
	lib/audit/user_action.rb
Merge remote-tracking branch 'origin/devel' into feature/audit_api_access

Conflicts:
	app/models/user_action.rb
	db/schema.rb
Merge branch 'devel' into feature/audit_api_access

Conflicts:
	app/models/user_action.rb
	db/schema.rb
Merge pull request #394 from 18F/feature/audit_api_access

audit API access and writes