Send bitcoins to address

        :param wallet_id: bitgo wallet id
        :param address: bitcoin address
        :param amount: btc amount in satoshis
        :param split: create new outputs if needed
        :return: boolean

def send(self, wallet_id, passcode, address, amount, message='', fee=None, fan_unspend=10):
        """
        Send bitcoins to address

        :param wallet_id: bitgo wallet id
        :param address: bitcoin address
        :param amount: btc amount in satoshis
        :param split: create new outputs if needed
        :return: boolean
        """
        MINIMAL_FEE = 20000
        MINIMAL_SPLIT = 10000000

        wallet = self.get_wallet(wallet_id)

        if not wallet['spendingAccount']:
            raise NotSpendableWallet()

        if not wallet['isActive']:
            raise NotActiveWallet()

        if amount < 10000:
            raise Exception('amount to small')

        if wallet['confirmedBalance'] < amount:
            raise NotEnoughFunds('Not enough funds: balance %s amount %s' %
                                 (wallet['confirmedBalance'], amount)
            )

        change_address = self.create_address(wallet_id, chain=1)
        usableKeychain = False
        spendables = []
        chain_paths = []
        p2sh = []
        payables = [(address, amount)]
        keychain_path = ""

        for keychain in wallet['private']['keychains']:
            keychain_path = keychain['path'][1:]
            keychain = self.get_keychain(keychain['xpub'])
            if 'encryptedXprv' not in keychain:
                continue
            usableKeychain = True
            break

        if not usableKeychain:
            raise BitGoError("didn't found a spendable keychain")

        data = json.loads(keychain['encryptedXprv'])
        #add base64 paddings
        for k in ['iv', 'salt', 'ct']:
            data[k] = data[k] + "=="
        cipher = sjcl.SJCL()
        xprv = cipher.decrypt(data, passcode)

        unspents = self.get_unspents(wallet_id)
        unspents = filter(lambda u: u['confirmations'] > 0, unspents['unspents'][::-1])

        total_value = 0
        for d in unspents:
            path = keychain_path + d['chainPath']
            chain_paths.append(path)
            p2sh.append(h2b(d["redeemScript"]))
            spendables.append(Spendable(d["value"],
                                  h2b(d["script"]),
                                  h2b_rev(d["tx_hash"]),
                                  d["tx_output_n"]))

            total_value += d['value']
            if total_value > amount:
                break

        # make many outputs?
        if len(unspents) < 5 and (total_value > (amount + MINIMAL_SPLIT)) and fan_unspend > 0:
            fee = self.calculate_fee(len(spendables), fan_unspend)
            value = (total_value - amount - fee) / fan_unspend
            for i in range(fan_unspend):
                payables.append((change_address, value))
        elif total_value > (amount + MINIMAL_FEE):
            # add a change address
            if fee is None:
                fee = self.calculate_fee(len(spendables), 2)
            value = total_value - amount - fee
            if value > 10000: #avoid dust
                payables.append((change_address, value))

        p2sh_lookup = build_p2sh_lookup(p2sh)

        spendable_keys = []

        priv_key = BIP32Node.from_hwif(xprv)

        spendable_keys = [priv_key.subkey_for_path(path) for path in chain_paths]

        hash160_lookup = build_hash160_lookup([key.secret_exponent() for key in spendable_keys])

        tx = create_tx(spendables, payables)

        tx.sign(hash160_lookup=hash160_lookup, p2sh_lookup=p2sh_lookup)

        r = requests.post(self.url + '/tx/send', {
                'tx': tx.as_hex(),
                'message': message
            }, headers={
                'Authorization': 'Bearer %s' % self.access_token,
            })

        return r.json()