Enhance file transfer styles

File transfer styles have been enhanced.

![progress](https://f.cloud.github.com/assets/41547/992690/e6206260-0984-11e3-9bfb-dcd435c6aaba.png)

Received file transfers are also now differentiated from sent ones:

![capture decran 2013-08-20 a 12 59 15](https://f.cloud.github.com/assets/41547/992790/c986ac2e-0987-11e3-870a-a86b396c97aa.png)

Last, I've extracted the verbose template code to a `<script type="text/template">` tag within the `chat.html` file.

I didn't feel specific tests were needed for this, though as I'm just back from holidays, I'm possibly too lazy and wrong :)