Remove pytest-flake8 plugin, use native cli

Author: Saurabh Kumar

.travis.yml

@@ -12,7 +12,8 @@ install:
   - pip install -q -r requirements.txt
   - pip install --editable .
 script:
-  - pytest -v --tb=native --cov --flake8
+  - flake8 .
+  - pytest -v --tb=native --cov
 after_success:
   - coveralls
 deploy:

requirements.txt

@@ -4,6 +4,5 @@ sh>=1.09
 bumpversion
 wheel
 pytest-cov
-pytest-flake8
 click
 ipython