v6.0.0

Changed

• Prefer const over var in README (@ralphtheninja)
• Upgrade abstract-leveldown dependency from ^5.0.0 to ^v6.0.0 (#68) (@ralphtheninja)
• Upgrade standard devDependency from ^11.0.0 to ^v12.0.0 (@ralphtheninja)
• Use full link references in README (#60) (@vweevers)

Added

• Explain serialization (#72) (@vweevers)
• Add nyc and coveralls (#64) (@ralphtheninja)

Removed

• Remove node 9 (@ralphtheninja)
• Remove now superfluous _setupIteratorOptions() (@ralphtheninja)