Return correct positions

[ZaneA]

In the API there are three different positions to consider, these are:

• tab(X/Y) - The raw position in tablet coordinates.
• pos(X/Y) - The position in screen pixel coordinates.
• sys(X/Y) - The position in screen coordinates, taking subpixels into account.

Currently all three positions are set as the tablet coordinates. While this doesn't seem to break anything, I'm pretty certain that it's incorrect. However I'm not sure if pos/sys should be screen coordinates or browser coordinates (and the Wacom docs are a little ambiguous here), and there will be other factors to take into account for both (multiple-monitors, browser position/size).

[ZaneA]

As of 13a73660148a8f1636bf86a783faaca8159ec49c posXY and sysXY are being returned as screen pixel coordinates. Seems to be more correct, but none of the examples I can find actually make use of it. Closing for now, but will need enhancements in the future (multi-monitor etc).