Travis: Use newer boost version

.travis.yml

@@ -6,11 +6,18 @@ compiler: gcc
 
 addons:
   apt:
+    sources:
+      - ubuntu-toolchain-r-test
+      - boost-latest
     packages:
-      - libboost-all-dev
+      - g++-5
+      - gcc-5
+      - libboost1.55-all-dev
       - libcurl4-openssl-dev
       - cmake
 
+install: export CXX="g++-5" CC="gcc-5";
+
 script:
   - cd TriviaBot
   - cmake .