Time Range Switching and README updates

Got time switching in, so now you can see your total time for total, last 7 days or the current day. I also took some time today to add to the README file, including some new images and some better instructions on how to use the app, and what features there are. As I said in the last devlog, I only have one more feature I need to add before shipping! Hopefully I can get that done in the next couple of days!