Update .travis.yml

Author: jeanlego

.travis.yml

@@ -1,8 +1,8 @@
+dist: trusty
+sudo: required
 language: c
 before_install:
 - sudo apt-get update -qq
-- sudo apt-get dist-upgrade -qq
-- sudo apt-get update -qq
 - sudo apt-get install -qq   - build-essential libx11-dev cmake flex bison ctags clang
 compiler:
   - clang