Fix/pep8 (#277)

* re-organized imports according to pep8
* fixed all remaining pep8 issues
* moved common config into setup.cfg, additionally test `tests`
* removed --select=X -- the errors selected where by default not in
  flake8's --ignore list so effectively had no effect
* update .travis.yml to reflect changes in tox.ini
* make travis just use tox in order to avoid code duplaction
* replace py.test with pytest
* fixed .travis.yml
* try different pypy toxenv
* hopefully fixed testenv for pypy
* added pypy basepython, removed unused python2.6
* install dev package before testing (fixes missing coverage)
* fixed empty exception pass blocks with noqa
* Added dummy log message on empty try-except-pass blocks to make dodacy happy :(
* Replaced Exception with BaseException

sshuttle/ssnet.py

@@ -4,6 +4,7 @@ import socket
 import errno
 import select
 import os
+
 from sshuttle.helpers import b, binary_type, log, debug1, debug2, debug3, Fatal
 
 MAX_CHANNEL = 65535