Add generator for handling config
Add documentation for generators
Set generator to use Devise scope in strategy setup
Warn users about database_authenticatable
Improve handling of strong_parameters vs. mass_assignment_security
Refactor OTP generation into its own function.

This will make it easier to integrate with SMS.
Merge pull request #3 from ShaneWilton/shanewilton/generators

Add a generator for installing devise-two-factor