Document jpathdir option in Python binding (#1150)

Author: danipozo

doc/ref/bindings.html

@@ -128,6 +128,7 @@ <h2 id="python_api">Python API</h2>
         Keyword arguments to these functions are used to control the virtual machine.  They are:
       </p>
       <ul>
+        <li><tt>jpathdir</tt>&nbsp;&nbsp; (string or list of strings)</li>
         <li><tt>max_stack</tt>&nbsp;&nbsp; (number)</li>
         <li><tt>gc_min_objects</tt>&nbsp;&nbsp; (number)</li>
         <li><tt>gc_growth_trigger</tt>&nbsp;&nbsp; (number)</li>