Try to fix Travis CI

.travis.yml

@@ -1,3 +1,5 @@
+sudo: required
+dist: trusty
 language: c
 notifications:
  irc:
@@ -19,17 +21,19 @@ addons:
    name: "pjanouch/ponymap"
    description: "Experimental network scanner"
   notification_email: p.janouch@gmail.com
-  build_command_prepend: "cmake .. -DCMAKE_BUILD_TYPE=Release -DWITH_LUA=OFF"
+  build_command_prepend: "cmake .. -DCMAKE_BUILD_TYPE=Release -DWITH_LUA=ON"
   build_command: "make"
   branch_pattern: coverity_scan
 compiler:
  - clang
  - gcc
 before_install:
+ # We need this PPA for Lua 5.3
  - sudo add-apt-repository ppa:ukplc-team/ppa -y
  - sudo apt-get update -qq
 install:
  - sudo apt-get install -y help2man libjansson-dev libncursesw5-dev
+   liblua5.3-dev
 before_script:
  - mkdir build
  - cd build