Allow embedded views to render; Fix TemplateDoesNotExist exception

When I tried to deploy f55d4 I found that for embedded links (labeled embed on each paste), views.py attempts to render_to_string 'embed.js', but embed.js doesn't exist in the repository.

Attempts to click the embed link returned a TemplateDoesNotExist exception.

I am not sure if there used to be an embed.js or if there is supposed to be an embed.js, but if instead I pointed everything at embed.html (and change the mimetype to match), things started working and the embed view properly rendered.