Bump travis Ubuntu from xenial(16.04) to bionic(18.04)

elichai · elichai · commit bc818b160cda · 2020-05-11T16:01:20.000+03:00
diff --git a/.travis.yml b/.travis.yml
@@ -3,6 +3,7 @@ os:
   - linux
   - osx
 
+dist: bionic
 # Valgrind currently supports upto macOS 10.13, the latest xcode of that version is 10.1
 osx_image: xcode10.1
 addons:
