Boost required version.

CMakeLists.txt

@@ -23,11 +23,13 @@ find_package(PythonLibs)
 include_directories(${PYTHON_INCLUDE_DIRS})
 
 if(DEFINED ENV{BOOST_ROOT})
-    message("-- BOOST_ROOT is set: $ENV{BOOST_ROOT}")
+    set(BOOST_ROOT "$ENV{BOOST_ROOT}")
+    message("-- BOOST_ROOT is set: ${BOOST_ROOT}")
 else(DEFINED ENV{BOOST_ROOT})
     message("-- Note: BOOST_ROOT not set.")
 endif(DEFINED ENV{BOOST_ROOT})
-find_package(Boost COMPONENTS python mpi filesystem serialization)
+message("-- BOOST_ROOT is set: ${BOOST_ROOT}")
+find_package(Boost 1.60.0 COMPONENTS python mpi filesystem serialization)
 include_directories(${Boost_INCLUDE_DIRS})
 
 find_package(MPI REQUIRED)