Add "application" alias to API object

By default gunicorn looks for an "application" object to run, so this
saves us having to type api:app.

README.md

@@ -28,7 +28,7 @@ Index the Solr statistics core to populate the PostgreSQL database:
 
 Run the REST API:
 
-    $ gunicorn dspace_statistics_api.app:api
+    $ gunicorn dspace_statistics_api.app
 
 Test to see if there are any statistics:
 

dspace_statistics_api/app.py

@@ -66,7 +66,7 @@ class ItemResource:
 def on_exit(api):
     print("Shutting down DB")
 
-api = falcon.API()
+api = application = falcon.API()
 api.add_route('/items', AllItemsResource())
 api.add_route('/item/{item_id:int}', ItemResource())