Fixed missing travis dependency for Ubuntu trusty

gstreamer1.0-plugins-base was removed in the updated 2017Q2 trusty image (https://github.com/travis-ci/build-environment-updates/blob/master/2017Q2/gce/garnet-trusty/dpkg-manifest.diff) and gir1.2-gst-plugins-base-1.0 does not depend on gstreamer1.0-plugins-base in trusty (fixed in xenial).

Author: kingosticks

.travis.yml

@@ -14,7 +14,7 @@ before_install:
   - "wget -q -O - https://apt.mopidy.com/mopidy.gpg | sudo apt-key add -"
   - "sudo wget -q -O /etc/apt/sources.list.d/mopidy.list https://apt.mopidy.com/jessie.list"
   - "sudo apt-get update -qq"
-  - "sudo apt-get install -y gir1.2-gst-plugins-base-1.0 gir1.2-gstreamer-1.0 python-gst-1.0 libffi-dev libspotify-dev python-all-dev"
+  - "sudo apt-get install -y gir1.2-gst-plugins-base-1.0 gstreamer1.0-plugins-base gir1.2-gstreamer-1.0 python-gst-1.0 libffi-dev libspotify-dev python-all-dev"
 
 install:
   - "pip install tox"