improve information emitted when skew is detected

Example output:

> Simulation time skew is 32.3%
> elapsed: 79572872070
>  simulated: 60.0
>  skew: 1.3  ~  1.1

While the first line is reasonably clear, the other lines are hard to interpret.  What unit is the "elapsed" in? Could this be converted to mm:ss or even just seconds, with a max of 2dp?  What are the two numbers on the final line?
