Travis CI: try to use conteiners

.travis.yml

@@ -1,3 +1,4 @@
+sudo: false
 language: c
 notifications:
  irc:
@@ -8,6 +9,11 @@ env:
  global:
   - secure: "LeuOo7WkygCR9BDkBv8ttWqSvL0TcEVnEYArBHmkBRZijOvI3EqyFeJMVPKCHt5JWXUmuaUnbNdK8FzYGGoMDGp6XP9NrHpVKCfN+ok9uRf2HftBjzH5SgMSP0H/dkDo24hBtFjlK/MXB7iDqiig0D80iEsvTP/5kjiWXv39Niw="
 addons:
+ apt:
+  packages:
+   - help2man
+   - libusb-1.0-0-dev
+   - libgtk-3-dev
  coverity_scan:
   project:
    name: "pjanouch/sensei-raw-ctl"
@@ -19,10 +25,6 @@ addons:
 compiler:
  - clang
  - gcc
-before_install:
- - sudo apt-get update -qq
-install:
- - sudo apt-get install -y help2man libusb-1.0-0-dev libgtk-3-dev
 before_script:
  - mkdir build
  - cd build