Added optinal tolerance value for numeric comparisons

The current implementation only does exact comparisons, there are certain situations(for example when different sources format floating point values differently) where you may want to add a tolerance to the numeric comparisons.  I added an optional tolerance parameter to the assertJsonEquals method(and of course method that method calls) that will return true if the two numeric values are within the given range.  I have added test cases that show my code works and I hope it can be incorporated into the main branch.

Thanks,

-Joel L. Tucci