Adapted from http://www.danvk.org/hex2dec.html
The problem is that parseInt("0x12345...") isn't precise enough to convert big integers correctly. This uses strings as input and, internally, arrays as workhorses.
This module exports a function, convertBase (this function is the module export), with a few shorthand methods (as properties of the exported function).
Converts a string representation of a number in base fromBase and converts it into a string respresentation in base toBase. That's it.
Shorthand for convertBase(input, 16, 10).
Shorthand for convertBase(input, 10, 16).
Shorthand for convertBase(input, 10, 2).
Shorthand for convertBase(input, 2, 10).
Shorthand for convertBase(input, 16, 2).
Shorthand for convertBase(input, 2, 16).