Travis: Get boost from PPA instead

Author: jonnor

.travis.yml

@@ -8,7 +8,8 @@ before_install:
 - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
 - sudo apt-get update -qq
 - sudo apt-get install g++-5
-- sudo apt-get install libboost-dev
+- sudo add-apt-repository ppa:boost-latest/ppa
+- sudo apt-get install libboost1.55-dev
 install:
 - npm install
 before_script: