Add quotes around incorrect command name

The problem I was facing was that I couldn't tell that I was typing
the wrong command.

diff --git a/moodle b/moodle
index 130f627..284dafb 100755 (executable)
--- a/moodle
+++ b/moodle
@@ -73,11 +73,11 @@ BIN=`resolve $COMMAND`
 
 if [ $? == 1 ]
 then
-    echo "Unknown Moodle command $1..."
+    echo "Unknown Moodle command '$1'..."
     exit 1
 elif [ ! -x "$BIN" ]
 then
-    echo "Permission denied. $BIN is not executable."
+    echo "Permission denied. '$BIN' is not executable."
     exit 1
 fi