v0.9

• Don't allow MapMutation.update() calls after the mutation is finished

• Simplify MapMutation.exit() implementation

v0.8

• Add new MapMutation.update() method that behaves like
  MutableMapping.update()

• Make it faster to create a Map() from another Map()—it's now an
  O(1) operation.

• update() method had a bug that could cause the update Map object to
  have a wrong number of elements.

v0.7

New Features

• All new APIs are covered in the README file.

• Allow Map objects to be constructed from other mappings:
  Map(a=1), or Map([('a', 1)]), or Map(dict(a=1)).

• Implement Map.update() method.

• Implement Map.mutate() and MapMutation API.

• Make Map objects pickleable.

• Make Map.keys(), Map.values(), and Map.items() proper dict-view
  like objects.

v0.6

• Fixed a crash in Map constructor (C implementation)

v0.5

• Reject keyword and positional arguments in new

v0.4

• Breaking change: Map.delete() now raises a KeyError if a user deletes a missing key.

• Add a pure-Python implementation to support PyPy.

• Test coverage is now 100%.

v0.3

• Implement Map.__repr__() and Map.__hash__()