CannonJS Plugin bug (v2.4)

Hi guys,

I upgraded to BabylonJS 2.4 and I think I've found a bug on the CannonJS plugin.

It's line 32 of babylon.cannonJSPlugin.ts:

this.world.step(this._fixedTimeStep, this._useDeltaForWorldStep ? delta * 1000 : 0, 3);

If I leave the default _useDeltaForWorldStep set to true, the game runs 1000 faster than normal, if I set it to false it works fine.

By removing the delta*1000 works as expected, resulting in this patch:

this.world.step(this._fixedTimeStep, this._useDeltaForWorldStep ? delta : 0, 3);

I can't do a PR at the moment, so I'm writing here... but I promise I will be able in the future!

Cheers,

Joez