Enable Account Locking

This enables the same functionality as the Devise Lockable extension, at the Authy code verification level. When configured properly, a user's account will be locked after too many failed verification code entries. It follows the same rules as the devise lockable extension, just applied to Authy code entry. 

What's New?
===
* DeviseAuthyLockable module. Provides logic for a model registered as a devise extension.
* AuthyLockable Feature RSpec coverage.
* Devise::Models::AuthyLockable RSpec coverage.


What's Changed?
===
* DeviseAuthyController - Failed attempt login has been moved to a method that either behaves normally, or performs the new locking logic.
* DeviseAuthyController RSpec tests updated.
* Additional helper methods in spec/support/helpers.rb.
* Rails App in Spec has additional routes, authentication tweaks to support lockable users in addition to non-lockable users.

What's Fixed?
===
* AuthyAuthenticatable RSpec tests have removed duplicate visit requests.