v0.7

New Features

* 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__()