Use compress_fst() in the RDS driver?

[wlandau]

Re #109 (comment) and #109 (comment), I think we could use compress_fst() + saveRDS(compress = FALSE) and see large speed improvements. All we need is a new compress_fst argument to storr_rds() and a tiny bit of logic. PR forthcoming. Should be much easier than #103, #108, and #109. Thanks @MarcusKlik for the idea!

[wlandau]

Hmm... should we use the existing compress argument for this?

[kendonB]

The package qs might also be useful as a backend.