Updated documentation in scales.h
Fixed weight reading to be properly-scaled double
Added documentation make target
Added License
Read and discard old packet
Added USB ID for USPS PS311

Thanks to Mike DePriest (mike.depriest@gmail.com), added a scale
definition for the USPS PS311 (made by Elane). ID is 7b7c:0100.
Simplified Makefile to use implicit rules
Updated contact information to include Github page.
Makefile: Fixed "lsscale" -> "lsusb"
Fixed gcc -Wall warnings
Added "Stamps.com Stainless Steel 5 lb. ..."
Made the number of valid scales a defined constant
Also add udev entry for stamps.com 5lb steel scale
Merge branch 'master' of https://github.com/erjiang/usbscale

Conflicts:
	Makefile
	usbscale.c
more