Fix site URL.

Maven needs to know the URL of the site once it is published, otherwise
some relative links won't work properly.

Author: gouttegd

pom.xml

@@ -6,7 +6,7 @@
 
   <name>ODK ROBOT plugin</name>
   <description>ROBOT plugin for the Ontology Development Kit</description>
-  <url>https://github.com/INCATools/odk-robot-plugin</url>
+  <url>https://incatools.github.io/odk-robot-plugin</url>
 
   <licenses>
     <license>