Add script to build serialport

Created interactive script to build serialport for node-webkit. This
script can be used after ```npm install``` is run. This should make it easier to get node-webkit working.
The x64 builds I'm talking about are the ones from Node-webkit. Linux x64 build is certainly doable, but a Windows x64 build is apparently not in the works, and building serialport as x64 for a 32bit application doesn't quite work.