update 'pyusb module is needed' message to make it clear that a version newer than 0.x is needed
expand commandline not found message to also mention that device not found can be casued be lack of permissions as well
add sample udev rules file for making the device file accessiable to non root users under Linux
Merge pull request #2 from alavaliant/master

Some minor updates to address common confusions/initial problems under Linux