Ignore system boost

.travis.sh

@@ -64,7 +64,10 @@ function configure()
       -DGTSAM_ALLOW_DEPRECATED_SINCE_V4=${GTSAM_ALLOW_DEPRECATED_SINCE_V4:-OFF} \
       -DGTSAM_BUILD_WITH_MARCH_NATIVE=OFF \
       -DCMAKE_VERBOSE_MAKEFILE=ON \
-      -DBOOST_ROOT=$BOOST_ROOT
+      -DBOOST_ROOT=$BOOST_ROOT \
+      -DBoost_NO_SYSTEM_PATHS=ON \
+      -DBOOST_INCLUDEDIR="$BOOST_ROOT/boost/include" \
+      -DBOOST_LIBRARYDIR="$BOOST_ROOT/lib"
 }