Add scaling of the y axis for demographic subgroup plots

[ccunningham101]

Keep the 0 min, but scale the max y value based on the max value in the measures file

[ccunningham101]

@milanwiedemann when we scale, should it always be from 0 to the max value, or should we go from the min to the max?

[milanwiedemann]

I think we either

1. set a fixed scale, which would almost always be 0 to 100% or
2. automatic scaling (using the default matplotlib settings)

[ccunningham101]

Nice, hadn't seen that feature! Made the switch