Link to most-recent version of static file (BB-3768)

AFAIK you can only link to a raw version of a file at a specific commit, like https://bitbucket.org/kevinburke/better-hn-filter/raw/d69537c2e068/LICENSE.

It would be nice if you could always link to the HEAD version of that file.

The URL could be:

https://bitbucket.org/kevinburke/better-hn-filter/raw/LICENSE

Or:

https://bitbucket.org/kevinburke/better-hn-filter/raw/head/LICENSE

It would be cool to if you could put tags in there where head goes, but head would be great at the moment.