fix: unit tests were using strict equality testing for numeric results; now check 15 decimals

The "exp" test in the Math unit tests was failing, despite expected and actual results being almost identical. I modified the assertEquals function to use 15 decimals of precision when comparing numbers, which seems reasonable based on discussion here:
http://www.w3schools.com/js/js_numbers.asp

I also tried 17 decimals, which still failed, and 16 decimals, which passed but I figured I'd be a little more conservative. All other math unit tests still pass.