Google Code-in

Read the bug report referenced. Don't get distracted but the statistics discussion and acronyms, this is actually a straightforward task.

1. Check that the patch from the bug report applies cleanly to the current code.
2. Edit the patch as suggested, to leave the Interpolate function in place, but not use it in the GetValue function.
3. Revise the documentation to state that this doesn't interpolate; it treats the CDF as a stepwise constant function.

Bonus work:

1. Rename Interpolate to DoInterpolate
2. Declare and implement a new public function virtual double Interpolate (double r). For implementation, look at what is done currently in GetValue(), and use that to find the correct values to call DoInterpolate with.