v2.2.1

This is critical bug fix for the 2.2.0 release. It fixes two issues:

• ClassCastException from Chunk#toArray (#1746)
• Restored binary compatibility with 2.1.0 release (#1747 #1748 #1749 #1750)

This release is binary compatible with all prior 2.x releases except for the 2.2.0 release, which should not be used.