replace 'precise' lib with something better

[joelmccracken]

Months ago I searched high and low for a good precise floating point math library in JavaScript, and I didn't find anything.

Since then, I have found a few:

https://github.com/dtrebbien/BigDecimal.js
https://github.com/MikeMcl/big.js

[joelmccracken]

http://blog.smartbear.com/testing/four-serious-math-libraries-for-javascript/