Part of slowly trying to bring all styles into a single CSS file.

Also, add urijs to more intelligently handle URIs

- Render images as thumbnails
- Use the image.html template when rendering images from pasted URLs
- Update message and spoiler markup to render avatars
- Use the default avatar as fallback when user doesn't have one
- Instead of 'me' render own name or JID

- Update the mockups to show avatars.

* Don't change styling based on media queries
* Fix offsets so that an embedded chat fits properly inside container element

Actually, it's used for rendering a MUC inside a webcomponent!

To make it more similar to how messages are sent in private chats and to
reuse methods as far as possible.

Removed `sendChatRoomMessage` and `clearChatRoomMessages`

* Fix typo which broke MUC file upload
* Remove unused method
* Move file input into li element

Updates #161

Update #161

updates #161

Also tweak progress indicator margin

updates #161