changes.md

Breaking changes:

• callContractMethod, move contractAddress param to be optional and to be after methodName
• subscribeToContractPendingTxs - rename to subscribeToPendingTxs and remove callbacks use it like that:

        subscribeToPendingTxs.on('data', txHash => {
            onData(txHash);
        })
        .on('error', error => {
            onError(error);
        });

• sendSignedTransaction - return RxJS instead of promise resolve/reject
• cancelPendingTx - last param is gasPrice addition, not customGasPrice like was before