flow.txt

- User opens browser window.
- Addon queries server for updates, and attempts to establish socket
  connection.
- User is notified of updates via Badge icon.
- User clicks addon icon and is directed to ideatown web client.
- On 'loaded' event, the addon sends down the update data, as well as
  currently installed addons.
- The client updates itself based on this data.(The user's browser
  should ALWAYS be the source of truth.)
- If there are conflicts, the addon should push an 'update' event to
  the server to update the model.
- We allow the user to select which addons they would like to
  install/remove and send the data to the addon.
- The addon will install/remove, send progress updates to the client,
  and send an 'update' event to the server.
- User navigates away from site.
- Hours later, an update is pushed and the user is notified again via
  ideatown icon badge. flow repeats.

                          +------------------------------------------+    
                          |   2. Send updates. 'handshake' complete. |    
  +-----------------------+-+                                        |    
  |         Server          |                                        |    
  +-------------------------+                                        |    
  |                         |      1. 'hello' fetch updates.         |    
  |                         |  <---    Establish Connection.         |    
  |                         |                    |                   |    
  |                         |                    |                   |    
  |                         |                    |                   |    
  |                         |                    |                   |    
  |                         |                    |                   |    
  |                         |                    |                   |    
  |                         |                    |                   v    
  +-------------------------+                    |                        
                                          +------+-----------------------+
                                          |            Addon             |
                                          +------------------------------+
 +------------------------------------->  |                              |
 | 5. Send ids of updates/removals        | 6. install/remove, send an   |
 |                                        |    update to server.         |
 |                                        |                              |
 |                                        |                              |
 |                                        |                              |
 |                                        |                              |
 |                                        |                              |
 |                                        +-------------------+----------+
 |                                                            |           
 |                                           ^                |           
 |                                           |                |           
++----------------------------+              |                |           
|           Client            |              |                |           
+-----------------------------+              |3. 'loaded'     |           
|                             +--------------+ (if conflict   |           
|                             |                send updates   |           
|                             |                to server      |           
|                             |                from addon)    |           
|                             |                               |           
|                             |                               |           
|                             |                               |           
|                             |                               |           
|                             | <-----------------------------+           
|                             |  4. Response to 'loaded'.                 
+-----------------------------+     {current: ['id3', 'id4'],             
                                     updates: ['id1', 'id2']}