Update: Android 2.4.1 release (app size reduction + exercise dropdown fix)

This release fixes a commonly-reported issue where people were having trouble using dropdown in exercises.  There are also a number of smaller bugfixes that should help the app run more smoothly.

We've also reduced the app size substantially!  Most users can expect reductions of around ~20-30%.  

The total effect for you will depend on your device and Android version.  But as an example, our in-house Nexus 6 download size went down to 7.4 MB (from ~13.9 MB two weeks ago!), and on-disk size was reduced to 26 MB (reduced by 10 MB!).