Live updating of slider

Hey there - amazing and concise work here!

I went ahead and changed your action target to be "touch drag inside" from "value changed"
"Value changed" only calls back on "touchEventsDidEnd", while "touch drag inside" is continuously updated.

I also went ahead and added a double ("currVal") to check against, so that the app only attempts to update the blur after a non-trivial slider move (1/range).
This can easily be changed, but is good to note so that people don't slam their processors with updates they won't see (cause you'll already be trying to blur to a new radius).

Finally, I added the readout for "value" to the slider, so you can read it now. (Before it just printed "Slider Value:")

Hope you dig, and thank you for your super helpful contribution to the open source iOS community.