Fixes#264
Implement the equivalent of java's String.hashCode on the conversation model.
Change avatar template and attributes. Use css classes for colors.
On the conversations list, if the last message is too long, cut it with ellipsis (...) instead of going out of the screen.
On the single conversation view, if the message in the bubble contains a word that is longer than a bubble, break it anyway instead of going out of the screen.
As a chrome packaged app, we have to keep at least one window open in
order to maintain our websocket connection in the background page.
This change replaces the system window frame with custom buttons in the
inbox header, such that the 'close' button merely hides the window
rather than unloading it.
Fixes#237
FREEBIE
