Add a .travis.yml for Travis CI

Add a .travis.yml for Travis CI

Installs all the build dependencies, and runs make check and
check-daemon.

V1: Based on Arun Raghavan's travis file. Added trusty repositories to get
newer libs.

V2: Explicitly list all dependencies instead of relying on the Ubuntu
package Build-Dependencies. Send notifications to pulseaudio-discuss

V3: Install libsystemd-daemon-dev, libsystemd-id128-dev,
libsystemd-journal-dev, and libsystemd-login-dev. Send notifications to
pulseaudio-commits. Drop libjson0-dev, libjson-c-dev is the package to
depend on.