Allow default boundary and capacity

[Dezzles]

Added support for a static withDefault() function that will attempt to pull defaults from global variables
Updated the visualize_qtree example to take advantage of this
Also updated dependencies to remove known security vulnerabilities (See commit messages)

[shiffman]

What if we call this something like create(). I do like this thinking, I think p5 beginners are pretty used to overloading? What if we allow something like:

QuadTree.create(); // defaults but throws error message if no p5?
QuadTree.create(x, y, w, h); // boundary with default capacity
QuadTree.create(new Rectangle(x, y, w, h), capacity); // for someone who wants full customization?

And maybe we should namespace everything? QuadTree.Rectangle, QuadTree.Boundary, etc.? Maybe just qt. or qt5. for short?

Thank you so so much fo taking a look at this!

[Dezzles]

Made the updates to support multiple different create functions, getting to the point that I think some more solid documentation needs to get put together. I'll take a look at that later this week. Raised a new issue for the namespace item ( #38 )

[shiffman]

This is awesome, thank you!