tweaks for older cmake

CMake/SuperBuild.cmake

         message( STATUS "pybind11 was found" )
     else()
         message( STATUS "pybind11 was NOT found, please build or remove LEMMA_PYTHON3_BINDINGS" )
+        find_package (Python COMPONENTS Interpreter Development)
 	    find_package(PythonLibs 3.0 REQUIRED)
         ExternalProject_Add(pybind11
 		    GIT_REPOSITORY "https://github.com/pybind/pybind11.git"
-		    GIT_TAG "v2.4.3" # "master" #"v2.4.3" #"master"
+		    GIT_TAG "v2.5.0" # "master" #"v2.4.3" #"master"
 		    UPDATE_COMMAND ""
 		    PATCH_COMMAND ""
     	    PREFIX ${CMAKE_CURRENT_BINARY_DIR}/external/pybind11