Merge pull request #3547 from lengau/patch-1

Update README.md to reflect move to RTD

Author: hpidcock

README.md

@@ -1,7 +1,7 @@
 # Documentation for Juju
 
-JUJU DOCUMENTATION HAS MOVED TO DISCOURSE:
+The Juju documentation is now on Read The Docs:
 
-https://discourse.jujucharms.com/t/documentation-migrated-to-discourse
+https://canonical-juju.readthedocs-hosted.com/en/latest/
 
 The bug tracker on GitHub is still active but as of March 18 2019 pull requests are no longer being processed.