Jquery less turtle

- removes jquery from turtle. (part one of #175)
- `__init__.js` almost completely linted
- removes unnecessary `Sk` references
- adds some tests to `Vector`
- fixes a bug that wouldn't let you draw just a circle.

@bnmnetp I know I changed a lot around. But there were a few very funky things going in in there I was wondering if you could test some stuff with this version. See if everything still works. It might be a good idea to see if we can write some tests for the turtle module with [jasmine canvas testing](http://humblesoftware.github.io/js-imagediff/test.html). It's probably also a good idea to see if we need the `Sk` refs in the `Turtle`, `TurtleGraphics` and `TurtleCanvas` classes. Seems to me to be logical to keep the `Sk` refs confined to the `$mod`. I looked for references to them in the skulpt code but they're probably for @runestoneinteractie right?