Changed new Thread() to use new AsyncTask()

Changed new Thread() to use new AsyncTask() - same as was done in src/org/thoughtcrime/securesms/service/KeyCachingService.java - https://github.com/WhisperSystems/TextSecure/commit/d97252d8d66c4927b2acf54c9b3ee290eac5a992
Merge pull request #260 from joeykrim/patch-2

Changed new Thread() to use new AsyncTask()