Replace deprecated methods

- #negative_failure_message => #failure_message_when_negated
Replace deprecated methods

- #mock => #double
Add travis setting
Use expect syntax in specs
Change rspec configurations

- Turn on raise_errors_for_deprecations! if config has a this option
- Remove treat_symbols_as_metadata_keys_with_true_values
Fix type miss

- raise_errors_for_deprecations -> raise_errors_for_deprecations!
Merge pull request #4 from rosylilly/rspec3

Be compatible with Rspec3