Pytest-automock

* prettify error message

* add support for mocking builtins
* add `--automock-remove` cli argument
* add support for targeting with module path
* fix coverage report on travis

* fix/add multiple instances support

Thanks to [Roman Tolkachyov](https://github.com/romantolkachyov)

* remove allowed/forbidden lists since complexity
* add result serialization to prevent mutations

* add python 3.6 support

* allow to override filename
* add black and white method lists
* add customizable encode/decode routines