force boost 1.55 install

.travis.yml

@@ -14,7 +14,7 @@ before_install:
   - sudo apt-get -qq update
   - sudo apt-get -qq install clang-3.9
   - sudo apt-get -qq update
-  - sudo apt-get -qq install build-essential libtool make cmake cmake-data openssl libzmq3-dev libboost-all-dev
+  - sudo apt-get -qq install build-essential libtool make cmake cmake-data openssl libzmq3-dev libboost1.55-all-dev
   - sudo apt-get -qq install libssl-dev libmysqlclient-dev libmysql++-dev libreadline6-dev zlib1g-dev libbz2-dev
   - git config user.email "travis@build.bot" && git config user.name "Travis CI"
   - git tag -a -m "Travis build" init