v0.2.0

New mpmc algorithm. Previous algorithm was based on block write counters - block's
len is updated when counter reaches 0. New one is based on bitblocks - each element
in block, have corresponding bit, and it is raised when write finished. The Number
of continuously raised bits is block's len. This ensures that readers will see their
messages ASAP, while maintaining message order. This requires less atomic stores
on the writer's side as well, so it is almost 30% faster!

See how it works.

Changed

• spmc and mpmc now have separate Readers.
• LendingItereator replaced with non-GAT LendingReader.

Added

• Readers now Cloneable.
• MIRI-friendly fuzzy testing.