Split-settings

Breaking changes:

- Drops `python2` support
- Drops `django2.0` support

Improvements:

- Moves to `poetry`
- Adds `mypy` support
- Adds `wemake-python-styleguide` support
- Adds extra CI checks: `safety`, `doc8`
- Adds `py.typed` file to package type information

Improvements:

- Added support for django till to 2.2 version.

Improvements:

- Added `Django==2.0`
- Removed old versions of `Django` from test matrix
- Removed `python3.4` from test matrix
- Documentation updates
- Adds more `flake8` plugins to enforce strict style

Bugs:

- Fixes Windows problems via [21](https://github.com/sobolevn/django-split-settings/pull/21)

Improvements:

- Added `python3.6` and `Django==1.11`
- Fixed `tests/settings` structure with `basic/` folder
- Added documentation, which is built with `Sphinx`
- Updated `README.rst` with new logo
- Updated `README.rst` with `docs` badge
- Updated `CONTRIBUTING.rst` with new information

Bugs:

- Updated `README.rst` to be compatible with `PyPI`

- Changed the default Django version in the requirements from `>= 1.5.1` to `>= 1.5`
- Added `setup.cfg` to support `python setup.py test` command
- Refactored how the tests work
- Added `tests/conftest.py` file with the fixtures, used fixtures widely
- Changed all test to be functions instead of classes
- Added new classifiers
- Added `pytest-env` to read env variables from `setup.cfg`
- Removed `run_coveralls.py`, added `after_success` section in `.travis.yml`
- Changed the `README.rst` to be shorter

- Added `django1.10` support
- Now `include` function finds parent `globals()` scope automatically if not provided
- Added protection against infinite recursion
- Added tests for stackable settings definition. See `tests/settings/stacked/`
- Added tests for the new functionality
- Added tests for `django1.10` in `tox` and `travis`
- Removed `3.2` and `3.3` from `setup.py` since these versions were not tested anyway