Install and configure RSpec - #2

- Install rspec-rails gem;
- Generate binstubs for rspec-core gem.
Force RSpec 'expect' syntax - #2

The 'expect' expectation syntax is being kind of a better practice in RSpec
community, so why don't use it.
Install and configure Cucumber - #2

- Install cucumber-rails gem;
- Install database_cleaner gem;
- Generate binstub for cucumber gem.
Install FactoryGirl - #2
Merge branch 'tests' into next