MINIFICPP-312: Update travis yaml file to manually install xz
MINIFICPP-312: Update travis yaml file to manually install xz

This closes #194.

Signed-off-by: Bin Qiu <08d2b2533c6fcd6c2678b11859cc3bfcd03b6c1c@gmail.com>

phrocker/nifi-minifi-cpp,apiri/nifi-minifi-cpp,jdye64/nifi-minifi-cpp,benqiu2016/nifi-minifi-cpp,achristianson/nifi-minifi-cpp,jdye64/nifi-minifi-cpp,apiri/nifi-minifi-cpp,apiri/nifi-minifi-cpp,minifirocks/nifi-minifi-cpp,NiFiLocal/nifi-minifi-cpp,minifirocks/nifi-minifi-cpp,NiFiLocal/nifi-minifi-cpp,benqiu2016/nifi-minifi-cpp,phrocker/nifi-minifi-cpp,phrocker/nifi-minifi-cpp,minifirocks/nifi-minifi-cpp,jdye64/nifi-minifi-cpp,dtrodrigues/nifi-minifi-cpp,benqiu2016/nifi-minifi-cpp,jdye64/nifi-minifi-cpp,NiFiLocal/nifi-minifi-cpp,NiFiLocal/nifi-minifi-cpp,achristianson/nifi-minifi-cpp,minifirocks/nifi-minifi-cpp,apiri/nifi-minifi-cpp,dtrodrigues/nifi-minifi-cpp,jdye64/nifi-minifi-cpp,phrocker/nifi-minifi-cpp,kevdoran/nifi-minifi-cpp,kevdoran/nifi-minifi-cpp,kevdoran/nifi-minifi-cpp,apiri/nifi-minifi-cpp,dtrodrigues/nifi-minifi-cpp,dtrodrigues/nifi-minifi-cpp,kevdoran/nifi-minifi-cpp,kevdoran/nifi-minifi-cpp,achristianson/nifi-minifi-cpp,dtrodrigues/nifi-minifi-cpp,phrocker/nifi-minifi-cpp,achristianson/nifi-minifi-cpp