Rider alerts now working again.
Fixed crash when no external (sdcard) storage available.
Bumped target SDK version to 18 from 16.

Change-Id: Iaa4b969dd5809a8f05575333e08ecf2a6176912b
apk for 1.7.2, tagged as such. Version bumped in manifest.

Change-Id: I3e21b464824909ab82ef337b441fb28266cfe4b7