level is returned as None in hidpp10.py when the performanceMX mouse is
charging. Since the battery state is unknown when beeing recharged it
will now return "N/A".
Before it would crash becasue level was None and could not be inserted
using %d.
It should check for None specificly
Merge pull request #126 from slaveriq/master

Fixing a crash when level is type None
Added Smooth Scrolling to the Performance Mouse MX

I tested solaar with my Performance Mouse MX, and the smooth scrolling worked like a charm, I just need to find a way to make the scrolling speed slower now.
System is Linux Mint 15.
Update devices.md

Added a little bit of info for the M325
Merge pull request #139 from parkerlreed/patch-1

Update devices.md
Merge pull request #134 from FrederikNS/patch-1

Added Smooth Scrolling to the Performance Mouse MX