add --help flag message

cow.py --help shows help message explaining the application, as show in proj requirements.

Author: RaihanSharif

cow.py

@@ -6,9 +6,10 @@
 #  parse the args
 parser = argparse.ArgumentParser(
     prog="cowsay command line tool",
-    description="ASCII art of animals saying text supplied as argument")
+    description="Make animals say things")
 
-parser.add_argument("--animal", choices=cowsay.char_names)
+parser.add_argument("--animal", choices=cowsay.char_names, help="The animal to be saying things.")
+parser.add_argument("message", nargs='*', help="The message to say")
 
 args = parser.parse_args()
 # cowsay.cow(" ".join(sys.argv[1:]))