Add interface for Index.
Add default dict to constructor.
Update the index with an event.
Add clear operation to index.
Fix Index.update test case.
Add Index.delete operation.
Refactor event key construction in Index.
Add Index.get operation.
Don't add expired events to the index.
Return deleted event or None, if it does not exist.
Return the updated event, or None if the event is expired.
Move un-implemented tests to the bottom of Index tests.
Move IndexTestCase.create_event to base test class.
Add protocol for len() and bool() to Index.
Add simple event expiry.
Whitespace.
Whitespace.
Rewrite expiry tests.
Expire events if their age is equal to the expiry time.
Add basic benchmark script for Index.