release-v1.0.3

• Reorganize atomicity of update operations across all segments.
• Make iterators auto refreshable.
• Lazy initialize iterators' internal segment iterators.
• Add manual refresh capability to the iterators.
• Added ZoneTree is disposing event.
• Added new disk segment is activated event.
• Implemented shorter lock region for merge operation.
• Automatically dispose iterators when the tree is disposing.

Full Changelog: release-v1.0.1...release-v1.0.3