Add Devise support for RSpec

As seen in https://github.com/plataformatec/devise
Fix duplication conflict on factory user's email
Group gems by environment
TDD flow setup = Guard + Spork

Just run `% guard` and test will be run when files are modified.

Removed test folder to solve conflicts with spork
http://stackoverflow.com/questions/8177331/problems-with-guard-spork-rspec-rails-3
Fix flash[:notice] call error

Also converts flash message to i18n cc: @faridh