Configurando ambiente de testes

closes #15
Então tranquilo. Comentei mais por ser uma prática que o próprio Rspec encoraja:

> Given that it is always loaded, you are encouraged to keep this file as
  light-weight as possible. Requiring heavyweight dependencies from this file
  will add to the boot time of your test suite on EVERY test run, even for an
  individual file that may not need all of that loaded. Instead, make a
  separate helper file that requires this one and then use it only in the specs
  that actually need it.