Added releasing signing files to .gitignore
Check if talk fragment still exists when talk details are loaded.

Fixes #1.
Use constant String when getting arguments for TalkListFragment
Keep track of quietly unfavorited talks to make sure they are not added to the list more than once.

Fixes the "Duplicate favorites" issue.
Removed unused activity labels from manifest.
Added Dutch translation of String resources.
Show Dutch versions of Parse resources.
Added support for "keynote" type talks.

Keynotes are always marked as a favorite, and get a pretty yellow background in the list of talks.
Updated build script for release 0.9.1