document how force=no works for win_get_url and add RETURN

lib/ansible/modules/windows/win_get_url.py

@@ -47,7 +47,10 @@ options:
     description:
       - If C(yes), will always download the file.  If C(no), will only
         download the file if it does not exist or the remote file has been
-        modified more recently than the local file.
+        modified more recently than the local file.  This works by sending
+        an http HEAD request to retrieve last modified time of the requested
+        resource, so for this to work, the remote web server must support
+        HEAD requests.
     version_added: "2.0"
     required: false
     choices: [ "yes", "no" ]
@@ -109,3 +112,15 @@ $ ansible -i hosts -c winrm -m win_get_url -a "url=http://www.example.com/earthr
     proxy_username: 'username'
     proxy_password: 'password'
 '''
+RETURN = '''
+url:
+    description: requested url
+    returned: always
+    type: string
+    sample: 'http://www.example.com/earthrise.jpg'
+dest:
+    description: destination file/path
+    returned: always
+    type: string
+    sample: 'C:\Users\RandomUser\earthrise.jpg'
+'''