Update README.rst

Adding an additional Command line usage step

README.rst

@@ -76,6 +76,12 @@ and/or optionally choose the filename (``-f`` or ``--filename=``):
 .. code:: bash
 
    $ pytube -e mp4 -f Dancing Scene from Pulp Fiction http://www.youtube.com/watch?v=Ik-RsDGPI5Y
+   
+You can also specify a resolution or desired filetype:
+
+.. code:: bash
+
+   $ pytube -e mp4 -r 720p http://www.youtube.com/watch?v=Ik-RsDGPI5Y