...this is the standard way to sign messages in bitcoin-qt. Note that the
format of a compressed signature, for messages, is quite distinct from DER
format, which is used in transactions. This commit also adds support for
recovering the public key from a signature, which is necessary for this. The
code for public key recover is taken from bitcoinjs-lib.
...no longer relies on Manuel's repo hostig a version of "bignum" that actually
contained bignumber.js. This moves bignumber.js internally and removes bignum
from the browser build process. Also adds a bitcore.Bignum that links to the
right thing. In node, browser.Bignum is require('bignum'). And in the browser,
bitcore.Bignum is is now Bignumber.js (same as before ... except bignumber.js
is now inside bitcore).