Merge branch 'master' into pyup-update-wheel-0.31.1-to-0.32.0

diff --cc requirements.txt
index 6688b7ee985a8045cf6ce942b0160cd66b735bc1,ec5610e3536a029df2e857934ca29a125eb12c76..74ac88b0a8a28cba111ee1889f948d8f41e427b0
--- 1/requirements.txt
--- 2/requirements.txt
+++ b/requirements.txt
@@@ -1,7 -1,7 +1,7 @@@
  # Testing and deployment packages.
  coverage==4.4.2
- pytest==3.7.4
+ pytest==3.8.1
  pytest-cov==2.6.0
  freezegun==0.3.10
- twine==1.11.0
- wheel==0.32.0
+ twine==1.12.1
 -wheel==0.31.1
++wheel==0.32.0