Pluggable backend support?

[sonic182]

It may be interesting see how it performs with different backends, I'm thinking in goleveldb (or the C++ implementation + cgo) and/or rocksdb

[aleybovich]

@sonic182 my advice - implement it yourself and send @valinurovam a PR, shouldn't be very hard. I almost added pluggable backend support myself as I needed a memory-only backend, but then I found that buntdb can support :memory: with some code changes. I simply made those changes and created a PR which Alexander merged. It's the fastest path.