gitignore: Don't ignore all dotfiles
Use prospector for static analysis rather than flake8

Prospector is a cover-all static analysis tool that runs the same tools
as flake8, plus a number of others including pylint.
Ignore a couple of false-positive pylint warnings
Remove unreachable code

This code was "removed" shortly before launch when the realtime features
were disabled. This commit removes this code entirely rather than
leaving dead and unreachable code in the repository.

This commit will probably be reverted in due course.
Merge pull request #1676 from hypothesis/pylint

Replace flake8 with prospector