Update pyproject.toml because coverage 5.0 has been released

[jlubken]

Move coverage configuration from setup.cfg to pyproject.toml.

See feature here: nedbat/coveragepy#664

Figure out how to represent exclude_lines in the toml file, because toml has a structured syntax unlike setup.cfg.

[djesic]

Came across this issue while looking for a solution myself.
This worked for me:

[tool.coverage.report]
exclude_lines = [
  "raise NotImplementedError",
  "def __repr__",
  "if __name__ == .__main__.:",
]

[jlubken]

Thanks! Updated in branch add/api.

[jlubken]

Completed.