Fix resource leak issue of cursor

Unclose cursor exists.
Rework of previous fixing.

Rework of previous fixing.
Merge pull request #395 from cloudrick/Rick's-local

Fix resource leak issue for cursors.
Dead code elimination FacebookDialog.java

I wish that I could be of help to you, but... :put_litter_in_its_place:
Merge pull request #399 from srea/dev

Dead code elimination FacebookDialog.java
Support ContextWrapper objs with LoginButton.

This particular change enables support for Mortar-based apps, which
render views using a context wrapper.
Merge pull request #401 from stevenle/dev

Support ContextWrapper objs with LoginButton.
Add missing import android.content.ContextWrapper
Merge pull request #402 from CristianOliveiraDaRosa/dev

Add missed import android.content.ContextWrapper
Facebook Android SDK 3.21
Facebook Android SDK 3.21

Summary:
    see https://developers.facebook.com/android/change-log-3.x/

Upgrading:
    https://developers.facebook.com/docs/android/upgrading/