Don't always return state and don't assign state object

[tschaka1904]

This is removing any state = * assignments and unnecessary return state. Part of #37

The reducer/s will take the state without state being manually assigned. The return is only needed, if we actually want to replace the entire state (e.g. state = action.props or state = merge(x, y))

[moromis]

Have you verified everything works, especially stuff like the opacity slider? If it does I'll approve this, I just thought I had to return for some reason (though that's not usually how Redux works, for sure)