show without args: show all
show/load can accept:
    * list of integers
    * negative numbers, meaning we count from the end of history list
    * number ranges (e.g. 2-7, -20-9, -29--9)
    * 0 means "start of the list", (e.g. 0-2 prints the first 2,
        -3-0 prints the last 3, etc)
    * all of the above seperated with spaces
    * order maters, repetitions allowed (show that history-load can behave
        like a script)