flake8 reqs: Update flake8-pep3101 to 0.4

- Rename pep8 to pycodestyle.
- Add support for python 3.5.
- Add flake8 pypi classifier.
- Drop python 3.3 and 3.4 support (only testing it probably works just
  fine).
- Fix travis and coveralls to work properly with python 3.5.

misc/requirements/requirements-flake8.txt

@@ -8,7 +8,7 @@ flake8-deprecated==1.0
 flake8-docstrings==0.2.8
 flake8-future-import==0.4.3
 flake8-mock==0.2
-flake8-pep3101==0.3
+flake8-pep3101==0.4
 flake8-putty==0.3.2
 flake8-string-format==0.2.2
 flake8-tidy-imports==1.0.1