Update .travis.yml

.travis.yml

@@ -13,17 +13,13 @@ matrix:
     - python: "2.7"
     - python: "3.4"
     - python: "3.5"
-before_install:
-    # Tricks to avoid matplotlib error about X11:
-    # 'no display name and no $DISPLAY environment variable'
-    # http://docs.travis-ci.com/user/gui-and-headless-browsers/#Starting-a-Web-Server
-    - "export DISPLAY=:99.0"  
 # command to install dependencies
 install:
 # add new stuff to requirements file, not here
   - pip install -r requirements.txt
 # command to run tests
 script:
+  - xvfb-run make test
   - python -m pytest --cov=gastop/
 
 after_script: