Browserify RIPEMD160

[dcousens]

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
• Only 1 more step to removing convert completely
• Increased Node.js (local) performance

I added some test vectors for RIPEMD160 to ensure basic functionality, although it was already been cross-tested by hash160.

[coveralls]

Coverage decreased (-0.0%) when pulling f0370ef on dcousens:ripemd into 0198477 on bitcoinjs:master.

[kyledrake]

Awesome!