slight docs fixes
- added with_any to stubs
- docs for with_any
- tests for with_any
- mocks now returns the stub rahter than a mock proxy
- chained stubs does not cary method visibility anymore
- chained stubs now have arguments-vary behavior
- updated stubs tests
- enhanced stubs docs
- stubs, protected_stubs and private_stubs as a way to stub multiple methods at once