disable line break warnings in pycodestyle

This commit disables warnings W503 and W504. One of these was added to the
default ignore list because it wasn't clear, and line breaks conflict with
another rule which doesn't allow lines greater than 80 chars. I believe that
disabling these rules (W503 + W504) is the cleaner solution.

See also discussion here: PyCQA/pycodestyle#498

.travis.yml

@@ -13,4 +13,4 @@ script:
   - py.test -svv test/unit/
 
   # style guide check
-  - find ./lib ./test ./bin -name \*.py -exec pycodestyle --show-source --ignore=E501,E402,E722,E129 {} +
+  - find ./lib ./test ./bin -name \*.py -exec pycodestyle --show-source --ignore=E501,E402,E722,E129,W503,W504 {} +