I just tried setting up the modules listed at http://developer.android.com/google/play/expansion-files.html today, but play_apk_expansion/downloader_librarycould not be imported as indicated.
play_apk_expansion/downloader_library/project.properties
:
android.library.reference.1=../market_licensing
android.library.reference.1=../../play_licensing/library
.. /
File -> New -> Import Module... play_apk_expansion/downloader_library, . play_licensing/library library, .