IEx.History
Function append/3
Appends one entry to the history.
Function each/2
Enumerates over all items in the history starting from the oldest one and
applies fun to each one in turn.
Function init/0
Initializes IEx history state.
Function nth/2
Gets the nth item from the history.
If n < 0, the count starts from the most recent item and goes back in time.
