Setuptools-scm

- fix 286 - duo an oversight a helper function was returning a
generator instead of a list

- fix a regression from tag parsing - support for multi-dashed
prefixes - 284

- fix a regression in setuptools_scm.git.parse - reorder arguments so
the positional invocation from before works as expected 281

- introduce pre-commit and use black
- print the origin module to help testing
- switch to src layout (breaking change)
- no longer alias tag and parsed_version in order to support
understanding a version parse failure
- require parse results to be ScmVersion or None (breaking change)
- fix 266 by requiring the prefix word to be a word again (breaking
change as the bug allowed arbitrary prefixes while the original
feature only allowed words\")
- introduce an internal config object to allow the configuration for
tag parsing and prefixes (thanks to \punkadiddle for introducing it
and passing it through)

- enhance docs for sphinx usage
- add symlink support to file finder for git 247 (thanks Stéphane
Bidoul)
- enhance tests handling win32 (thanks Stéphane Bidoul)

- fix 237 - correct imports in code examples
- improve mercurial commit detection (thanks Aaron)
- breaking change: remove support for setuptools before parsed
versions
- reintroduce manifest as the travis deploy can\'t use the file finder
- reconfigure flake8 for future compatibility with black
- introduce support for branch name in version metadata and support a
opt-in simplified semver version scheme