0.15.5

Additions

• Add argument reverse to iterate and listAll to allow almost instant
  queries for "last x transactions matching query y".
• Reduce lock time on writing new transactions.
• Optimize the logic of writing new transactions.

Fixes

• Make sure the results of iterate and listAll are returned in insertion
  order, or reverse insertion order if reverse is set.

Full Changelog: 0.15.4...0.15.5