fix typo in documentation url
@@ -43,7 +43,7 @@ Documentation?
xhtml2pdf has some documentation, and we could use your help improving it.
A good place to start is ``doc/usage.rst``.
-Or also see in `Readthedocs <http://xhtml2pdf.readthedocs.io//>`__
+Or also see in `Readthedocs <http://xhtml2pdf.readthedocs.io/>`__
Call for testing
