Use guard-rspec with bundler
Support conversion to be_truthy / be_falsey

This closes #8.
Add -b/--boolean-matcher option
Add boolean matchers to supported conversions section in README
Use rspec 2.99 ready projects in test tasks
Refactor with Project class
Abort if the project's rspec is older than version required by Transpec
Convert boolean matcher only if target project's rspec is 2.99 or later
Support conversion to allow(obj).to receive_messages(:message => value)

This closes #6.
Merge branch 'rspec-3'