Switch to container-based Travis infrastructure

.travis.yml

@@ -1,5 +1,16 @@
 language: python
 
+# Setting sudo to false opts in to Travis-CI container-based builds.
+sudo: false
+
+# The apt packages below are needed for sphinx builds
+addons:
+    apt:
+        packages:
+            - graphviz
+            - texlive-latex-extra
+            - dvipng
+
 python:
     - 2.6
     - 2.7
@@ -65,12 +76,6 @@ before_install:
     - export PATH=/home/travis/miniconda/bin:$PATH
     - conda update --yes conda
 
-    # UPDATE APT-GET LISTINGS
-    - sudo apt-get update
-
-    # DOCUMENTATION DEPENDENCIES
-    - if [[ $SETUP_CMD == build_sphinx* ]]; then sudo apt-get install graphviz texlive-latex-extra dvipng; fi
-
     # Make sure that interactive matplotlib backends work
     - export DISPLAY=:99.0
     - sh -e /etc/init.d/xvfb start