Add activesupport for String#classify in tests.
Ignore switch_file.
Add cucumber and aruba.
Pass Scenarios:
  Scenario: Verified instance doubles
  Scenario: Unverified instance doubles
  Scenario: Verified class doubles
  Scenario: Unverified class doubles

  Implemented calls: should_receive, with, and_return

  Known issues:
  * and_return assumes one return value
  * `it verifies_contract: "<method_signature>" {}` is not recognized.