Fix Travis build errors

[waltjones]

Werkzeug (1.0) and mock (4.0) are recently released major version releases that caused a variety of travis issues. Also, python 3.3 needs to run on trusty now, which required a few setup changes.

• Ubuntu Xenial can't find Python 3.3 any longer. Try using Trusty.
• Some 3.x versions don't work well with mock, so use unittest.mock.
• Implicit conversion using dict() changes behavior in python >= 3.6.
• Ensure tested setuptools version. (Trusty doesn't have setuptools by default, and latest setuptools (45.x) produces errors that need to be addressed.)
• Python 3.3 needs a compatible werkzeug version (0.14.1).