Clean up comparison assertions

Using assertTrue and the comparison operators to test
if an element is greater, equal, or less is too python2.4.
Our unit testing framework 'testtools' supports
- assertEqual
- and testtools Matcher classes
which were created for these types of tests.

Re-implemented assertGreater and assertGreaterEqual
with compatibility for python < 2.7.

Change-Id: I6f3e3279630393e594c75d30cb4b895c2e2c22ca
Merge "Clean up comparison assertions"