Added a new Mutation Slider to the top right of the screen over the Color Picker. 

The slider changes the Mutation Rate of new fungus being spawned, both with left and right click. The mutation rate effects differ for each fungus, but around 1/4th of the bar, or 0.25 is a 'default' setting. If you crank it all the way to the right, at 1, you're bound to get some really wild Fungus, including some that might take up the entire screen and could result in some flashing colors, so be careful!