Fixed bug with regions not working correctly after load() with time series

Hello,
I've encountered a bug with rectangular regions in a time series.
The problem was that after passing data to load() and specifying regions via myChart.region([...]) these regions were not visible. When I looked into generated HTML, regions were there but had weird positions: around -9000000, because it used parsed Date for calculations - probably casted to string, not numeric values of Date. Placing valueOf() resolved this problem.

That's one thing - another one could be an example of using regions with timeseries, because at first I didn't know my start and end values should be based on time (I tried to pass chart point id's, like in the example on website)

I've also generated new c3.js and c3.min.js generated from grunt - I don't know if I should. Maybe a contribution guide would be nice? :)