update to truthy falsey
Merge pull request #373 from rspec/switch_to_truthy_matchers

Switch to be_truthy and be_falsey
Remove deprecated file.
Merge pull request #376 from rspec/remove_old_spec_mocks_file

Remove deprecated file.
Add verifying double features from rspec-fire.

This is intended to be both API compatible with rspec-fire, and to
completely obsolete it.

Fixes #227.