Browserify RIPEMD160

This pull request switches from `Crypto-JS`'s RIPEMD160 to the one now shipping with `crypto-browserify`.
This is preferred for two reasons:

* We want to move away from `Crypto-JS` eventually
* Consistent usage of Buffer
* So close to removing `convert` completely

I added some test vectors for `RIPEMD160` to ensure basic functionality, although it was already been cross-tested by `hash160`.