travis: pull liblz4-dev from wily

.travis.yml

@@ -2,13 +2,13 @@ language: cpp
 sudo: required
 dist: trusty
 before_install:
- - sudo add-apt-repository 'deb http://archive.ubuntu.com/ubuntu/ vivid main' -y
+ - sudo add-apt-repository 'deb http://archive.ubuntu.com/ubuntu/ wily main universe' -y
  - |
-   sudo sh -c '/bin/echo -e "Package: *\nPin: release n=vivid\nPin-Priority: 1" > /etc/apt/preferences.d/vivid'
+   sudo sh -c '/bin/echo -e "Package: *\nPin: release n=wily\nPin-Priority: 1" > /etc/apt/preferences.d/wily'
  - sudo apt-get update -qq
 install:
  - sudo ./prepare-release travis-ci
- - sudo apt-get -qq -y -t vivid install gettext
+ - sudo apt-get -qq -y -t wily install gettext liblz4-dev
  - make
 script:
  - make test