startRangingBeaconsInRegion should check range ID

[Vandalko]

Long-running app may call "startRangingBeaconsInRegion" a significant number of times.
There's no internal check if such range is already present resulting in unlimited array growth.

I think the correct behavior should be to replace the existing (same ID) region.

[davidgyoung]

@Vandalko. I did a quick check and you are absolutely right. I am surprised that it has been this way for so long! This does not seem to have caused any problem reports that I am aware of, but it would still be good to fix.

I'd welcome a pull request if you are up for it.