Add re-authentication warning

CHANGELOG.md

@@ -5,6 +5,8 @@ Changelog
 
 * Experimental 2FA support (#3)
 * Do not create a new application for each login
+* **Warning**: Due to changes in configuration format, after upgrading to this
+  version, you will be required to log in to your Mastodon instance again.
 
 **0.6.0 (2016-04-17)**
 

README.rst

@@ -14,6 +14,10 @@ Interact with Mastodon social networks from the command line.
    :target: https://pypi.python.org/pypi/toot
 
 
+.. warning::
+   Upgrading to version ``0.7.0`` will require you to log in to your chosen Mastodon instance again.
+
+
 Installation
 ------------