Maintenance release

- Pulls in upstream change to use raw strings for regex
- Updates to how the package builds, tests, and runs lint
- Uses PEP 517/518 metadata for build requirements/backend
- Formatting improvements, including use of isort

Version v20181111:

- Rename module to diff-match-patch to supercede existing PyPI module
- Match existing module version scheme
- Update readme, tests, etc for import names

Bug fix v2018.11.06.1:

- Remove pathlib import from setup.py to fix py2 builds

Release v2018.11.06:

- Add support for Python 2.7 using conditional imports.
  Includes the upstream python2 implementation and tests,
  and selects them at import time as appropriate.

Initial release v2018.11.05