Travis: fixed import of numpy

Author: Clement Champetier

.travis.yml

@@ -82,8 +82,10 @@ addons:
     - python-dev
     - python-imaging
     - python-numpy
+    - python-scipy
     - python-nose
     - python3-dev
+    - python3-numpy
     - python3-setuptools
     - python3-nose
     - libfreetype6-dev