[#9] ensure that callback is a function (defined) before setting up it

this was breaking it on OSX/Safari …
[#349] restore the viewport.setBounds function (but now with more parameters)
[#349] updated the example to use the setBounds function
[#349] set the default bounds values to Infinity
Fixed/Simplified the `me.Rect.union` function
[#312] added a `getBounds` function to object containers calculating the bounds based on all child bounds
Updated `grunt-contrib-jshint` to version 0.8.0 (uses jshint 2.4.0)

Don't forget to do a `npm install` :P
Updated jsdoc to version 3.2.2

although version 3.3 will probably be out by the time we release melonJS
1.0.0 :)
documentation fix
[#369] completely removed collisionBox and now properly use `getBounds` when required