Fix for Issue 21

Fix for Issue 21, Is.InRange Constraint Ambiguity

I added unit tests to test the reversed range parameters plus some boundary conditions, then fixed the code to pass the tests and updated the documentation.

Based on comments on the issue, I decided to throw an ArgumentException if `from` was less than `to`. I also decided that the range should be inclusive of the boundaries since that was the way it was currently written. I added tests for these boundaries.