add WalletKey required dependency
Buffer.concat expects an array of buffers
util is in bitcore/util/util.js - fixes all uses of util
valueNum needs to be in satoshis, but datastore.outputs[addrStr] is in bitcoins
get rid of redundant util -> replace with coinUtil
add write_datastore after signing for a wally wallet

...requires proper handling of asynchronous rpc call, hence adding async.js as
a required package.
allow scripthash & multisig to be signed more than once
don't append serialized script if it's already there
sometimes scriptSig.chunks has length 0
fix bug where you had to sign with 3rd key first
bring p2sh multisig in line with BIP 0011

1) remove placeholders when a p2sh multisig transaction has been fully signed.
2) prepend the script with OP_0
https://github.com/bitcoin/bips/blob/master/bip-0011.mediawiki
https://github.com/bitcoin/bips/blob/master/bip-0016.mediawiki
move script functions to bitcore
Merge pull request #4 from ryanxcharles/bug/multisig-bugs

write signed transactions for wally wallets, plus several bug fixes
replace tabs with spaces
convert to buffertools 2.0 and fix concat error
allow cosign to be included as module

...check to see if it is "main" like in python
wrap cosign in class so that testing is possible
remove debug console.log
add proof of concept test, only tests constructor
add test for main(), along with useful test modules