Proposal to further rubify Nature of Code Examples

Well I could not resist messing with your code, and I think you've done a nice job. However feel free to reject entirely this pull request, but I hope you find it interesting. I would suggest some changes are made to fit with the ruby-processing ethos of preferring ruby to java. Such as replacing random(1, 3) with 
rand(1 .. 3.0) the 3.0 makes sure floats are generated rand(1 .. 3) produces integers, this can be useful in some of the examples. Also 99f7de9d8919f5433df2e6d3bf9c8eef7a1efdae fixes an error food should be left where bloop died.  Although I prefer to use vecmath Vec2D and Vec3D over PVector, I can understand if you prefer to keep PVector.  However Vec2D really came into its own in the perceptron examples, allowing for much more functional code (even more ruby like code).