Updated README

Author: yhirose

README.md

@@ -7,6 +7,8 @@ A C++11 single-file header-only cross platform HTTP/HTTPS library.
 
 It's extremely easy to setup. Just include **httplib.h** file in your code!
 
+NOTE: This is a 'blocking' HTTP client/server library. If you are looking for a 'non-blocking' library, this is not the one that you want.
+
 Server Example
 --------------