Upgrading devise from 2.3.3 to 3.0.0

* Changed user migration
* Replaced devise gem with 3.0.0 form 2.3.3:x
Adding Roles and optimizing stuff

* Added multiple roles support.
* Making stuff configurable.
* Adding more fields in User table.

TODO:
Merge pull request #2 from slade1/souranil/optimizing_stuff

Souranil/optimizing stuff