Add transmission support for 802.15.4 modules

It shouldn't break compatibility - but since there are no tests, you maybe want to check by hand if it breaks anything before merging it.

So for those with Series 1/802.15.4 modules, just add ```module: '802.15.4'``` to the xbee-promise option array and be sure to use destination16/destination64 instead of destinationId when using ```remoteTransmit```.