In Julius Caesar, Act I, what does the soothsayer tell Caesar in Scene 2, and how does Caesar respond?

In Act I Scene 2, the soothsayer says only one short line
to Caesar, but he says it twice.  The line is the famous saying, "Beware the Ides of
March" (line 20).  The Ides of March is March 15, so the soothsayer (a fortune teller)
is warning Caesar that something bad will happen to him on that day.  Caesar pays little
attention to him.  In fact, he couldn't even hear him at first, hence the reason why the
soothsayer repeated himself.  Caeser quickly dismisses him by saying "He is a dreamer. 
Let us leave him.  Pass!" (line 25).

Though Caesar ignores
the soothsayer, he ends up running into him again in Act III, Scene I. Caesar remembers
the Soothsayer's warning and says, "The Ides of March are come" (line 1).  Caesar is
basically mocking the soothsayer because his warning didn't hold up.  The Soothsayer
replies, "Ay, Caesar, but not gone" (line 2).  Of course, a few hours later, Caesar is
killed and the soothsayer is vindicated.