Welcome mail template
* Config different layout for devise
* Zoho Mail
* Add allowed param to model
Rails4 move strong_parameter to controller so we should change too
* welcome email
* Email template for welcome
Close #44
* Add Omniauth gem, twitter and github
* Support login with Github
* Get rid of credit card when register. Close #41
* When logging via 3rd service, assig noty-silve plan to user by default
* However, not able to handle the case oauth user has the same email with a existed user.