Add ulid module for object representation of a ULID.
Add ulid module for object representation of a ULID.

The four types defined here are as follows:

* MemoryView: Wraps memoryview/bytes to provide common base.
* Timestamp: Represents first 48 bits of ULID.
* Randomness: Represents last 80 bits of ULID.
* ULID: Represents entire 128 bits of ULID.

ahawker/ulid