travis: Test on Ubuntu 14.04 infrastructure

This change also minimizes the set of Python packages installed with APT
so that we're testing against the latest PyPI releases when possible.

.travis.yml

@@ -1,18 +1,11 @@
-sudo: false
+sudo: required
+dist: trusty
 
 language: python
 
 python:
   - "2.7_with_system_site_packages"
 
-addons:
-  apt:
-    sources:
-      - mopidy-stable
-    packages:
-      - graphviz-dev
-      - mopidy
-
 env:
   - TOX_ENV=py27
   - TOX_ENV=py27-tornado23
@@ -20,6 +13,11 @@ env:
   - TOX_ENV=docs
   - TOX_ENV=flake8
 
+before_install:
+  - "sudo sed -i '/127.0.1.1/d' /etc/hosts"  # Workaround tornadoweb/tornado#1573
+  - "sudo apt-get update -qq"
+  - "sudo apt-get install -y graphviz-dev gstreamer0.10-plugins-good python-gst0.10"
+
 install:
   - "pip install tox"