Add dependence on matplotlib

.travis.yml

@@ -19,7 +19,7 @@ before_install:
   - sudo apt-get install -qq python-opencv libcv-dev libcvaux-dev libopencv-dev
   - if [ -n "${NUMPYSPEC}" ]; then sudo apt-get install -qq libatlas-dev libatlas-base-dev liblapack-dev gfortran; fi
   - if [ -n "${NUMPYSPEC}" ]; then pip install --upgrade pip setuptools; fi
-  - if [ -n "${NUMPYSPEC}" ]; then pip install --find-links http://wheels.astropy.org/ --find-links http://wheels2.astropy.org/ --use-wheel numpy$NUMPYSPEC sphinx nose; fi
+  - if [ -n "${NUMPYSPEC}" ]; then pip install --find-links http://wheels.astropy.org/ --find-links http://wheels2.astropy.org/ --use-wheel numpy$NUMPYSPEC sphinx nose matplotlib; fi
   - pip install cpp-coveralls
 install:
   - "python bootstrap.py"