Likely that the deprecation warning from cryptography is causing the
setup.py sphinx build command to return an error so the tox/travis job
is marked as failing. Changing to calling the sphinx-build command
directly solves this.
Also updated the sphinx config for built-in napoleon and faster builds
using jobs option.
* Removed unused mock dep
* Modified flake8 to run entire codebase (fixed exclude)
* Change isort to shows files that need attention (no diff)
* Uniform layout for tox.ini
* Change flake8 complexity to 15