Support pen input in editor (Win 8 tablets)

There are quite a few users reporting that the new windows 8 tablet pen inputs (e.g. the Surface Pro) don't work with the Unity editor. I don't know if its a big ask, but for users with those devices, this is most disappointing. It would be great to see this fixed.

http://answers.unity3d.com/questions/410968/unity-wont-work-on-win-8-surface-pro.html