Updated README and enabled Proguard code shrinking

Changed README to give the correct setup instructions for Android Studio, including fixed for some current glitches in Android Studio. (I spent a few very frustrating hours trying to import into Eclipse as recommended by the current instructions!)

Configured proguard to shrink the code, and enabled proguard in both debug and release mode. The project was failing to run because of the Dalvik method limit as discussed here:
http://stackoverflow.com/questions/15209831/unable-to-execute-dex-method-id-not-in-0-0xffff-65536

Apparently the measurements library used in Units.java has changed, so I did a minor syntax fix there.