Ability to zoom

[gingerbeardman]

It's difficult to see what colour pixels the histogram is made up of when the game isn't doing much.

It'd be nice if the vertical axis could scale to fill, or be adjustable in some other way.

[englercj]

Totally, feel free to put in a PR. I don't really have the time to be working on this project much anymore. Too many things going on atm.

The reason I did it this way originally was because if it was that low it didn't matter what it was. Only when it got bigger did it matter and at that point you could see.