This was used to conditionally render messages in the group style, but
it's actually unnecessary. We can render the same markup in both cases
and change the appearance with css.
Move base64 encoding of attachments to an AttachmentView. This makes
image rendering an asynchronous task so we fire an update event to
indicate to the parent MessageListView that its content has changed
height and it is time to scroll down.
Getting up and running with IndexedDB was pretty easy, thanks to
backbone. The tricky part was making reads and writes asynchronous.
In that process I did some refactoring on Whisper.Threads, which
has been renamed Conversations for consistency with the view names.
This change also adds the unlimitedStorage permission.
This dependency may be a little heavy for our current use case, but we can
roll with it for now and find something slimmer if it turns out yagni.
Closes#77Closes#40
