Clarified build instructions

dlib/cmake_utils/add_python_module

@@ -97,9 +97,9 @@ if (NOT Boost_FOUND)
         message(STATUS " When it completes, set BOOST_LIBRARYDIR equal to wherever b2 put the compiled libraries.")
         message(STATUS " Note that you will need to set the address-model based on if you want a 32 or 64bit python library.")
         message(STATUS "")
-        message(STATUS " Next, when you invoke cmake to compile dlib you may have to use cmake's -G option to set the ")
-        message(STATUS " 64 vs. 32bit mode of visual studio.  Also, if you want a Python3 library you will need to ")
-        message(STATUS " add -DPYTHON3=1.  You do this with a statement like: ")
+        message(STATUS " Next, if you aren't using python setup.py then you will be invoking cmake to compile dlib.  ")
+        message(STATUS " In this case you may have to use cmake's -G option to set the 64 vs. 32bit mode of visual studio. ")
+        message(STATUS " Also, if you want a Python3 library you will need to add -DPYTHON3=1.  You do this with a statement like: ")
         message(STATUS "    cmake -G \"Visual Studio 12 2013 Win64\" -DPYTHON3=1 ..\\..\\tools\\python")
         message(STATUS " Rather than:")
         message(STATUS "    cmake ..\\..\\tools\\python")