initial commit

address, base58, base58check, hash all working with tests.

base58check code taken from bitcore.
add big number support

Extend bn.js with some convenience methods. Extension code taken from bitcore.
remove ripemd160 dep., replace with hash.js
point
expose buffer
rename redundant point.pointFromX to point.fromX
privkey
pubkey
random

...code from bitcore
standardize capitalization in test describes
use hash marks in function names in tests
buffer is a dependency
use process.browser only, which is sufficient
key
signature
ecdsa
make "new Point()" work
add tests for all ecdsa functions
refactor privkey
make address more consistent with rest of lib