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
Add letter_opener to show emails in the browser
Add capybara support for RSpec
Notify user about confirmation link when signing up
Test sign up flow

By using capybara we prove that user will receive a message about
the confirmation link needed to complete the sign up process.
Merge pull request #4 from Intngbl/auth-flow-specs

TDD setup + auth-flow specs