molecule scenario to test upgrading from releases

Provide a separate scenario to install the last release, then update to
the current one.
Also includes improved deployment verification (check if uploading a
.txt through the API works).

ansible/molecule/default/verify.yml

@@ -1,14 +0,0 @@
----
-# This is an example playbook to execute Ansible tests.
-
-- name: Verify
-  hosts: all
-  gather_facts: false
-  tasks:
-  - name: check if webserver is up
-    uri:
-      url: http://localhost:8000
-      status_code: [200, 302]
-      return_content: yes
-    register: landingpage
-    failed_when: "'Sign in</button>' not in landingpage.content"