Bug 840069 [Messaging:MMS] Update compose input to div[contentEditable] for media display, create ThreadUI.compose object to handle placeholder, events, etc
Bug 840069 [Messaging:MMS] Add unit tests for placeholder, expose dom elements more cleanly, and add more interface methods
Bug 840069 [Message:MMS] Add Attachment constructor to hold data and render display element. Manage attachments in ThreadUI.compose, retreive message content as an array of text and attachments, and exposeinterface to attach. Unit tests included.