add custom fmt and datefmt to LogFormatter
Speed up gen.corouting when yielding done Futures
Reset state on `start()` end
Document the attributes required by @run_on_executor.

Closes #933.
Avoid a quote mark that renders incorrectly in PDF mode.

Closes #935.
Merge pull request #931 from SuminAndrew/LogFormatter-format

add custom fmt and datefmt to LogFormatter
Update docs for LogFormatter constructor arguments.
Make setuptools optional again in setup.py.
Merge pull request #940 from klaussfreire/master

Speed up gen.corouting when yielding done Futures
Merge pull request #944 from anton-ryzhov/reset_flags

Reset state on `start()` end