Use crypto-js as a module from npm

Current crypto-js is partially ported from 2.0.0 and partially ported from 3.2.1(modified to use 2.0.0's interface). The npm [crypto-js module](https://github.com/evanvosberg/crypto-js) is up-to-date. I hope to get the benefit of bug fixes & features from upstream by using the module. Also, applications that uses bitcoinjs-lib and cryto-js do not have to worry about two different implementations for the same set of cryto functions.

The downside of the module is that the source is uglified, so it isn't very debugging friendly.

@abrkn @kyledrake thoughts?