Add s3ql

[fanzalika]

No description provided.

[fd0]

Hm, that's not a backup program, or is it?

[fanzalika]

It can be used as backup too, have de-duplication in its internal.

[cfcs]

It sounds like it can be thought of as a FUSE interface to a backup program.
They do list off a bunch of buzzwords (deduplication, encryption, ...), the programming language its written in, etc - it would be nice if you could add the relevant tags so we stay somewhat consistent with the other entries.