Build, package and publish pre-compiled binary versions for serial port ...

...using node-pre-gyp

Add fallback to buil to node-pre-gyp install command, in case remote binary download fails.

Added travis automated binary build, to generate and pubslish the serialport packages.

Publish binaries adding `[publish binary]` to a commit message or by
adding a release tag.

Add travis automated build for x86 32 bit binaries.[publish binary]