Fixed import for postprocessor threading

headphones/postprocessor.py

@@ -13,8 +13,11 @@
 #  You should have received a copy of the GNU General Public License
 #  along with Headphones.  If not, see <http://www.gnu.org/licenses/>.
 
+from __future__ import with_statement
+
 import os
 import time
+import threading
 import music_encoder
 import urllib, shutil, re
 from headphones import notifiers