Make edx-tim install itself so that the XBlock registers.

.travis.yml

@@ -2,8 +2,8 @@ language: python
 python:
   - "2.7"
 install:
-  - "pip install -r requirements/base.txt --use-mirrors"
   - "pip install -r requirements/test.txt --use-mirrors"
+  - "pip install -e ."
 script:
   - "python manage.py test"
   - "python manage.py harvest"