Fixed description of voxel-to-world matrix.
Merge pull request #66 from tsherif/comment-fix

Fixed description of world-to-voxel matrix.
Created util captureTouch. Surface Viewer now uses captured mouse/touch.
Added basic touch controls to Volume Viewer.
Added touch zoomcontrols to Volume Viewer.
Tweeked panning speed.
Merge pull request #68 from tsherif/touch

Touch controls for Volume Viewer. Closes #64.