switch to the new container based infrastructure

.travis.yml

@@ -4,13 +4,21 @@
 language: csharp
 mono: 3.12.0
 
-# Don't use the container based infrastructure
-sudo: true
+# http://docs.travis-ci.com/user/migrating-from-legacy
+sudo: false
 
 cache:
   directories:
   - thirdparty/download
 
+addons:
+  apt:
+    packages:
+    - nsis
+    - nsis-common
+    - dpkg
+    - markdown
+
 # Environment variables
 env:
   secure: "C0+Hlfa0YGErxUuWV00Tj6p45otC/D3YwYFuLpi2mj1rDFn/4dgh5WRngjvdDBVbXJ3duaZ78jPHWm1jr7vn2jqj9yETsCIK9psWd38ep/FEBM0SDr6MUD89OuXk/YyvxJAE+UXF6bXg7giey09g/CwBigjMW7ynET3wNAWPHPs="
@@ -20,7 +28,6 @@ env:
 # Check source code with StyleCop
 # call OpenRA to check for YAML errors
 script:
- - sudo apt-get remove nuget # https://github.com/travis-ci/travis-ci/issues/3940
  - travis_retry make all-dependencies
  - make all
  - make check
@@ -50,7 +57,6 @@ notifications:
     skip_join: true
 
 before_deploy:
- - sudo apt-get install nsis nsis-common dpkg markdown
  - export PATH=$PATH:$HOME/usr/bin
  - DOTVERSION=`echo ${TRAVIS_TAG} | sed "s/-/\\./g"`
  - cd packaging