Serialize message signatures about ethereumjs-util

[axic]

@fanatid are r and s in two's complement format in secp256k1.sign()?

@kumavis I don't think the above should need to use fromSigned/toUnsigned conversion. Also it converts it to the format the new geth is using (the one uses v-27).

[kumavis]

this is just copy pasta from lightwallet https://github.com/ConsenSys/eth-lightwallet/blob/master/lib/signing.js
sorry im not very familiar with this one

[kumavis]

obv we should include a verify method

[fanatid]

@axic secp256k1.sign return r/s as unsigned numbers that lower than n (FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141)