Added a note to think about types early (When thinking about inputs and outputs)

Lectures/L04_ReqContinued/ReqContinued.tex

@@ -247,6 +247,8 @@ Also Goal Statements and Requirements
 \begin{itemize}
 \item Goal statement(s)
 \item Inputs and outputs
+\item Think about the types of your inputs and outputs (not everything is a real
+  number)
 \end{itemize}
 
 \end{frame}