Update README

Author: yhirose

README.md

@@ -4,7 +4,7 @@ cpp-httplib
 [![Build Status](https://travis-ci.org/yhirose/cpp-httplib.svg?branch=master)](https://travis-ci.org/yhirose/cpp-httplib)
 [![Bulid Status](https://ci.appveyor.com/api/projects/status/github/yhirose/cpp-httplib?branch=master&svg=true)](https://ci.appveyor.com/project/yhirose/cpp-httplib)
 
-A C++ header-only cross platform HTTP/HTTPS library.
+A C++ single-file header-only cross platform HTTP/HTTPS library.
 
 It's extremely easy to setup. Just include **httplib.h** file in your code!