update documentation to add beta install instructions

docs/source/whatsnew/version7.rst

@@ -33,6 +33,15 b' Make sure you have pip > 9.0 before upgrading. You should be able to update by s'
 
     pip install ipython --upgrade
 
+.. only:: ipydev
+
+  To update the beta version, run
+
+  .. code::
+
+      pip install ipython --upgrade --pre
+
+
 Or if you have conda installed: 
 
 .. code::