doc: improve readLine.pause()

The docs for readLine.pause are misleading. I seriously spent hours on this. If
it isn't a bug, at least it should be well documented.

Someone else stumbled on this too:
http://stackoverflow.com/questions/21341050/pausing-readline-in-node-js

Reviewed-by: Trevor Norris <trev.norris@gmail.com>
Reviewed-by: Chris Dickinson <christopher.s.dickinson@gmail.com>

doc/api/readline.markdown

@@ -125,6 +125,8 @@ Example usage:
 
 Pauses the readline `input` stream, allowing it to be resumed later if needed.
 
+Note that this doesn't immediately pause the stream of events. Several events may be emitted after calling `pause`, including `line`.
+
 ### rl.resume()
 
 Resumes the readline `input` stream.