ability to set alpha, strokeAlpha, and fillAlpha on pixi renderer
added regular polygon vertex helper
feature: renderers now automatically resize
feature re #37 methods transform world/body coords
added special debug renderer
added velocity-verlet integrator
added body sleeping
added options for sleeping, world.wakeUpAll()
added deep copy option to options helper
re #109, #108, #103. Major fixes to pixi renderer
fixes #132. pixi renderer handles body removal
fix: renderers now render points too
fixes #101. interactive behavior uses .applyTo
re #122. fixes multi-grabbing the same body
fixes #92. pubsub handles fns on prototype better
fixes #95. empty arrays handled
fix re #76. sweep prune had wrong aabb dims
fix for #76 polygon collision detection
fix: circle collisions without overlap were faulty
fix for pubsub priorities
fix for timestep rounding errors
bug fix: multiple calls to ticker.start fixed.
fix interpolation rendering on follow
documentation fix for #104
fix for issue #94
fix issue #99
safer window context fix