(#114) - cleanup of pouch.adapter.js

* comments about compaction added
* remove console.log
(#114) - add if for undefined seqs

We don't want to bother leveldb with deletion of undefined keys
as we don't have to
(#114) - deletions could be more parallel now
(#114) - make deletion parallel in idb

Make deletion requests parallel so that idb could process it somehow
faster.