Slightly tweak hw4 template file

src/homework/hw4/homework4.sh

@@ -12,12 +12,15 @@ function print_link {
 
 function problem1 {
   # Type your answer to problem #1 below this line
+  echo "Remove this line"
 }
 
 function problem2 {
-  # Type your answer to problem #1 below this line
+  # Type your answer to problem #2 below this line
+  echo "Remove this line"
 }
 
 function problem3 {
-  # Type your answer to problem #1 below this line
+  # Type your answer to problem #3 below this line
+  echo "Remove this line"
 }