More improvements for bip32

Previous api was breaking access to bip32key.getKey() for public keys, since internally the key was stored differently (as byte array instead of ECkey), forcing special casing in higher level api.

This changes (most in [0a7914f] with [0291fc5] and [5107030] adding some polishing and fixes)

Other improvements are included:
 * Added bitcoin addresses from test vectors into the mocha test [d7a0e0b]
 * Fixes one case of a variable that was being stored globally by error [5107030]