Enable 3.3 in Travis (works; see https://travis-ci.org/phihag/youtube-dl/jobs/3757443 )

.travis.yml

@@ -2,7 +2,7 @@ language: python
 python:
   - "2.6"
   - "2.7"
-#  - "3.3"
+  - "3.3"
 script: nosetests test --verbose
 notifications:
   email: