Check stability of `sorted()` code

[alanjds]

As pointed on #82 (comment), the sorting of lists are not respecting stability or comparison of types:

$ python -c 'print sorted([1,1.0,2,2.0], reverse=True)'
[2, 2.0, 1, 1.0]
$ grumpy -c 'print sorted([1,1.0,2,2.0], reverse=True)'
[2.0, 2, 1.0, 1]

The implementation should be checked.

[funny-falcon]

Problem is in current reverse option implementation. It should not be implemented as reversed(sorted(l)), but as negation of comparison function.