replace bignumber.js with bn.js
use elliptic in Point in the browser instead of cryptojs
use elliptic for Point.multiply  and key regeneration
update sign function to use elliptic
add "ECKey" to Key test so grepping is easier
remove cryptojs dependency from Key
remove cryptojs dependency from util

...use hash.js, which is already required by elliptic
remove cryptojs dependency

...and all vendor bundle files.
require Point ... woops
remoe unimplemented bignum.pow()
make bignum interface backwards compatible

- fix cmp, mul, div, add, mod, sub functions to take numbers and strings
- fix Point class to use common folder correctly
make bignum tests run in node, not just browser
woops - add bignum back to browser tests
use a decorate function to optimize bundle filesize
add tests to make sure bignum interface works correctly
use decorate on gt and lt
simplify use of bignum in util
remove commented-out code
uncomment part of TransactionBuilder test
add tests for toCompressedPubKey