Render messages as HTML when requested

Made required changes in app.py, so that raw messages can be rendered in html format when accept header is "text/html"
Also added raw.html to render these messages.

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Initially i was using fedmsg.meta modules but it didn't return the required output. This file (http://hastebin.com/rivenivaga.py) contains more about the output.

So finally i went ahead and done some cleaning in python dict and made the required changes to present messages in elegant way.
http://hastebin.com/civopaviku.django