v0.0.1

Changes

• Rename door.utilities.Resource to door.utilities.Proxy.
• Separate and move door.utilities.Door into door.doors.AcquirableDoor
  and door.doors.SAcquirableDoor.
• Separate and move door.utilities.AsyncDoor into
  door.doors.AsyncAcquirableDoor and door.doors.AsyncSAcquirableDoor.
• Remove door.primitives.AsyncPrimitive and
  door.primitives.FineGrainedAsyncPrimitive.
• Fix documentations.

Additions

• Add door.primitives.Waitable, door.doors.WaitableDoor,
  door.doors.AsyncWaitableDoor for conditional variables.
• Add door.utilities.await_if_available.