Feature support for animated updates

[zenangst]

• Add new Inject.animation that will be invoked when new source is injected into your application.

[zenangst]

@krzysztofzablocki Don't know if this is something you want but I find it helpful to notice if the injection was successful or not without having the look at the console, even if the current setup is very reliable.

[krzysztofzablocki]

that's cool, let's add that :)