Adding options for viewing stars (part of https://github.com/a2/PebbleBucks/pull/7)

(Second part of https://github.com/a2/PebbleBucks/pull/7)
After finally getting the login to work, I noticed that my stars were at 0. I found in the code that it is pulling the "amount of stars remaining until the next free drink". Since I'm currently a Green Rewards member, this will always be 0. It would be much more useful to me if I could see my current number of stars, though I know for others the original number is better.

I added in an option on the this gs-pages branch for choosing which star type you want to see (along with the back-end code for populating the dropdown and returning the value). I then added the necessary code to the pebble-js-app.js file in the master branch to pull the preference from the storage area and pull the appropriate star number from Starbucks.