Use crypto-js as a module from npm

[weilu]

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 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?

[kyledrake]

This is great, and I think we should pull this in!

I'm getting a failing test due to global leaks on the Signing and Verifying test:

Error: global leaks detected: v, k

Not sure how to fix that one.

[weilu]

My bad. Only ran the tests with mocha test because I was working on individual test files. I didn't know that --check-leaks is turned off by default. Should have remembered to run npm test before pushing.