add EventSource interface

[hussachai]

I just implemented Chat sample app using SSE but it's not in the package. So, I added one.
Ref.
http://www.w3.org/TR/2012/WD-eventsource-20120426/#the-eventsource-interface

[hussachai]

I'm sorry if I gave you too little information. The EventSource from MDN is not up-to-update.
So, I used W3C as a reference instead. I googled and found that there are 3 drafts from 2009,
2011, 2012. I used the latest one and tested with Chrome and Firefox.
You can see the implementation here
https://github.com/hussachai/play-scalajs-showcase/blob/sse/scalajs/src/main/scala/example/ChatJS.scala

The event type is not specified in W3C draft but I checked with 2 browsers as I mentioned above.
The settings parameter is supposed to be dictionary. I tried to use Map but it didn't work, so I used
js.Dynamic instead.

[lihaoyi]

Sorry, haven't taken time to look at this yet. Will get to it at some point when I have time to go familiarize myself with the spec.

I feel that I should at least understand what I'm merging before I merge it, which is why I haven't merged it yet =)

[hussachai]

Not a problem :)
I just want to give you more info about what I did. I hope it can save your time a bit.

[lihaoyi]

Looks good to me, thanks =)