* Pin flake8 to latest version 3.2.1
* Update passlib from 1.6.5 to 1.7.0
* Pin aiohttp to latest version 1.1.5
* Pin aiohttp-session to latest version 0.7.1
* Update aioredis from 0.2.8 to 0.2.9
* Pin pep257 to latest version 0.7.0
* Pin pytest-aiohttp to latest version 0.1.2
* Pin aiopg to latest version 0.12.0
* Pin pytest to latest version 3.0.4
* Pin sphinx to latest version 1.4.9
* Pin coverage to latest version 4.2
* Pin pytest-cov to latest version 2.4.0
