Fix bug 1111650 - Stop using wheels on Travis for the base dependencies.

This is a step backward to be able to take us in the right direction (bug 1054262).
Merge pull request #2956 from jezdez/bug1111650

Fix bug 1111650 - Stop using wheels on Travis for the base dependencies.
Merge branch 'master' of https://www.github.com/mozilla/kuma
[Bug 1093362] Download button placement issue is fixed