Update dev requirements
Update dev requirements

The following requirements were updated with pybot,
note the changes in requirements_dev.txt:
  - Update pip from 8.1.2 to 9.0.1
  - Update flake8 from 2.6.0 to 3.3.0
  - Update tox from 2.3.1 to 2.7.0
  - Update coverage from 4.1 to 4.4.1
  - Update sphinx from 1.4.8 to 1.6.3
  - Update cryptography from 1.7 to 2.0
  - Update pyyaml from 3.11 to 3.12

Author: 014ca7bb507255f115360f46141ad318dcf61352@pyup.io

ljvmiranda921/pyswarms,ljvmiranda921/pyswarms