Use ==/!= to compare str, bytes, and int literals (#767)

* Travis CI: Add more flake8 tests

* Use ==/!= to compare str, bytes, and int literals

./project_euler/problem_17/sol1.py:25:7: F632 use ==/!= to compare str, bytes, and int literals
			if i%100 is not 0:
      ^

* Use ==/!= to compare str, bytes, and int literals

* Update sol1.py