The text of the TypeError is different in Python 2 and 3.
Remove api docs that are no longer needed.
Factor out duplicate parameter documentation.
Remove unused return values.
Remove vestiges of the ancient should_raise wrapper pattern.
Implement 'unless' parameter to ShouldRaise for some edge cases.
make doc docstrings again, rather than unused string expressions ;-)
Add license text.
Tweak to RoundComparison representation.
Re-order comparison docs.
Fix RoundComparison for Python 3.

In Python 3, rounding a number no-longer always returns a float, so the following is no longer true:

round(Decimal(1.12345), 2) == round(float('1.12345'), 2)

To be safe, RoundComparison now raises a TypeError if the rounded expected value is not of the same type as the rounded actual value.