added readme for cli

README.rst

@@ -174,6 +174,15 @@ change:
         return ImageBlockConverter(**options).convert(html)
 
 
+Command Line Interface
+=====================
+
+Use ``markdownify example.html > example.md`` or pipe input from stdin
+(``cat example.html | markdownify > example.md``).
+Call ``markdownify -h`` to see all available options.
+They are the same as listed above and take the same arguments.
+
+
 Development
 ===========