added scroll offset fix
Pulled some constants out of functions and made them variables at the top for easier tweaking.

Tweaked the upload interval to make drawing appear smoother.
Updated .gitignore to exclude the node_modules directory.
Merge git://github.com/ianharmon/drawthing
Bound mouseup and mouseleave to the document. The idea is to allow the user to continue drawing on the canvas even if the mouse temporarily leaves the drawing area, but he/she is still holding down the mouse.
Merge branch 'master' of github.com:drewaburden/drawthing