Merge branch 'master' into pyup-update-wheel-0.30.0-to-0.31.0

diff --cc requirements.txt
index 989a38bb6ac8889ae37581016f0811ee862abd22,42d88918551ec39e9440c381341a397e98819127..02b421c95c3e9ff2bfcf13d6e16310cf140f616a
--- 1/requirements.txt
--- 2/requirements.txt
+++ b/requirements.txt
@@@ -3,4 -3,5 +3,5 @@@ coverage==4.4.
  pytest==3.5.0
  pytest-cov==2.5.1
  freezegun==0.3.10
 -wheel==0.30.0
+ twine==1.11.0
 +wheel==0.31.0