greenio, tpool: python3 compatibility

Also:
- PEP-8
- check both EAGAIN/EWOULDBLOCK
- use system implementation of GreenPipe.readinto()
Python 3 compatibility fixes

Closes GH-102
Closes GH-103
Closes GH-104
wsgi: websocket: Reformat code + tests (PEP-8)
Travis: Enable fast build finish
tests: Update bundled mock library to 1.0.1
tests: ProcessBase -> run_python

Extracted inline code to permanent files
Python3 compatibility of test files
tests.run_python: new_tmp flag to create new temporary directory and
    pass it to child process via environ[TMP].
    The directory with any files is removed when child process is
    finished.
tests.rmtree: silent version of shutil.rmtree()