Try to get travis working again.

.travis.yml

@@ -4,9 +4,11 @@ os:
     - linux
     - osx
 
+sudo: required
+dist: trusty
+
 before_install:
     - if [ `uname` = "Linux" ]; then
-          sudo add-apt-repository ppa:gqrx/releases -y;
           sudo apt-get update -qq;
           sudo apt-get install -y build-essential debhelper librtlsdr-dev libusb-1.0-0-dev pkg-config;
       elif [ `uname` = "Darwin" ]; then
@@ -20,4 +22,4 @@ script:
       elif [ `uname` = "Darwin" ]; then
           make;
          make test;
-      fi
+      fi