removed double variable assignement in the `me.Rect` constructor
improved the collision test example

makes it easier to see the performance improvement on the long run, and
easier to visualize the quadtree implementation
fixed the debugPanel `drawMemoryGraph` function

this is still broken though, as the memory usage stat are not being
displayed...
Fixed the debug Panel velocity drawing

same issue that with the memory graph earlier :P
renamed functions to make them clearer. Added docs to canvas renderer init
merged in changes, fixed conflicts