UI accessibility fixes

I like CryptoCat and the idea of it, but it wasn't overly friendly to people using screenreaders in several regards. So I thought I'd spend my day off making it a lot nicer to use with a screenreader.

This fork, in a small amount of stuff written, does a fair few things:
* When tabbing to editable fields, a description is read out for the field (I think I got all of them). 
* When a message is received, it is automatically read allowed to the user if they have a screenreader active (like in other popular messaging apps)
* The send button now has a label
* The buttons at the top of the screen are detectable and readable with screenreaders now. Their labels to screen readers also change when the tooltips and similar change.
* The buddy list names now appear like links, to indicate their clickability
* The buddy menu dropdown button is now detectable with screen readers and has the appropriate aria markup for a dropdown menu button
* The buddy menu itself now has appropriate aria markup on its items

This might not look like much, but it does make CryptoCat much nicer to use with a screenreader, at least from my experience. There is more that could be done, but this is a good starting point.

This has only been tested with Firefox and [NVDA](http://www.nvaccess.org/) and only in group chats (as I can't test it with FB chat for some reason), but the theory is sound. I have access to other screen reader users who might be able to give a better picture how it plays with other screenreaders in other browsers.

I'd really appreciate if this came into CC, as it would make my (and hopefully many others) experience of it a lot better. I've been looking for a decent chat client to use with FB chat, and with these fixes, the cat could be the one