remove confusing (to me) `distribute_setup` bootstrap
add monkeypatch for broken `formatannotation` in `funcsigs`

...and pin `funcsigs` version dependency, to make sure we don't get a
later version, with which our monkeypatch might be incompatible.
add a 'real' README and LICENSE; remove unused docs
clean up and flesh out setup metadata
remove unused unit test dependencies :-(
fix missing import for `namedtuple`
demote `backports.inspect` from a package to a module
remove unused `funcsigs` vendor import

...because we're now getting it directly from PyPI and monkeypatching.