Discussion permalinks

# Open: Comment permalinks

We need permalinks to comments to work in NextGen.
They now do.

### Why?
People who wanted NextGen were being forced into the past when using comment permalinks. Through changing our permalink endpoint and adding a bit of functionality to NextGen, people can be where they feel more at peace... NextGen.

The format is:
`discussion.theguardian.com/comment-permalink/{{COMMENT_ID}} -> www.theguardian.com/{{ARTICLE}}#comment-{{COMMENT_ID}}`.

We have shifted a lot of the logic to the play app, making for a nice tidy client implementation.

![Oh yes](http://cdn2.sbnation.com/imported_assets/1427463/Al-bundy-ed-oneill-animated-gif-2.gif)