Update Travis-CI instructions

.travis.yml

@@ -17,8 +17,9 @@ before_install:
   - sudo add-apt-repository -y ppa:biometrics/bob.preview
   - sudo apt-get update -qq
   - sudo apt-get install -qq --force-yes bob-dev
-  - sudo apt-get install -qq python-opencv libcv-dev libcvaux-dev libopencv-dev
-  - if [ -n "${NUMPYSPEC}" ]; then sudo apt-get install -qq libatlas-dev libatlas-base-dev liblapack-dev gfortran; fi
+  - sudo apt-get install -qq --force-yes libjpeg8-dev libnetpbm10-dev libpng12-dev libtiff4-dev libgif-dev
+  - sudo apt-get install -qq --force-yes python-opencv libcv-dev libcvaux-dev libopencv-dev
+  - if [ -n "${NUMPYSPEC}" ]; then sudo apt-get install -qq --force-yes 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 matplotlib; fi
   - pip install cpp-coveralls