VeloC should target Boost 1.53 instad of 1.60

[tonyhutter]

It would be much easier for users if VeloC targeted Boost 1.53 instead of 1.60. 1.53 is included with RHEL 7 & CentOS 7, which is what a lot of sites are going to be running. Is there something absolutely essential to 1.60 that we can't get with 1.53?

$   cmake -DCMAKE_BUILD_TYPE=Debug -DWITH_KVTREE_PREFIX=`pwd`/install -DWITH_AXL_PREFIX=`pwd`/install .
CMake Error at /usr/tce/packages/cmake/cmake-3.9.2/share/cmake-3.9/Modules/FindBoost.cmake:1878 (message):
  Unable to find the requested Boost libraries.

  Boost version: 1.53.0

  Boost include path: /usr/include

  Detected version of Boost is too old.  Requested version was 1.60 (or
  newer).