Added Volumue percentage command

Hello I am not 100% sure how this whole pull request thing works.

I added Volume percentage command.
So they can say "volume 50"  to set volume to 50%.  Google Now got confused when I said Volume 50% or something so I told the user to not say the %.

I had to add to the build settings to get it to compile on my computer, but if it compiled without that on yours its probably easier if you ignore the gradle settings if you merge.