stupid typo

Author: pancetta

.travis.yml

@@ -30,7 +30,7 @@ install:
   - conda list
   - pip install --user coloredlogs
   - pip install --user travis-sphinx
-  - sudo apt-get install -y texlive-latex-recommended texlive-fonts-recommended texlive-latex-extra divpng
+  - sudo apt-get install -y texlive-latex-recommended texlive-fonts-recommended texlive-latex-extra dvipng
 
 script:
   - ./docs/update_apidocs.sh