To improve the startup time, lazy load and configure s3 stuff only when needed.
Add support for fragments in topic_link
Use topic_link for internal links
Fix typo
No need to apply the filter
Add something to automatically generate retina images
Get rid of unused images
Fixup automatic anchors
Retina image support:

Don't rebuild non-retina images if the retina version has not changed

* Fixup all screenshots
* Scale down only the bigger images (width > 900px)