Rewrite Biods_base in JavaScript
##The Origin of Boids
Boids is an artificial life program developed by Craig Reynolds to simulate the behavior of flocking birds. The name refers to the birdlike objects that populate the simulation. Instead of programming complex behavior for the boids, Reynolds provided three simple rules:
####Separation Each boid should stay away from its flockmates to avoid overcrowding.
####Alignment Each boid should move toward the average direction and with the average speed of its flockmates.
####Cohesion Each boid should move toward the average position of its flockmates.
His research made its way into a paper in ACM SIGGRAPH 1987, an annual conference on computer graphics, and has since been one of the most cited examples of the principles of artificial life.
##License
According to the book 《Exploring.Everyday.Things.with.R.and.Ruby》of chapter 7 examples.