Adds events for attachments

Signed-off-by: Akash Manohar J <akash@akash.im>

app/assets/javascripts/backbone/data/attachments.js.coffee

@@ -1,2 +1,23 @@
 class Kandan.Data.Attachments
-  # TODO use this for the file list plugin
+  @callbacks: { "change": [] }
+  @cache: []
+
+
+  @all: (callback)->
+    attachments = new Kandan.Collections.Attachments([], {
+      channel_id: Kandan.Data.Channels.activeChannelId()
+    })
+    attachments.fetch({ success: callback })
+
+  @registerCallback: (event, callback)->
+    @callbacks[event].push(callback)
+
+  @runCallbacks: (event, data)->
+    @cache = data.extra.attachments
+    callback(data) for callback in @callbacks[event]
+
+
+  @unregisterCallback: (event, callback)->
+    delete @callbacks[@callbacks.indexOf(callback)]
+    @callbacks.filter (element, index, array)->
+      element!=undefined