demo/modifiers.should: command-line --mod should override test modifiers

Opens #43.

demo/modifiers.should

-!OPTIONS: --mod w
 
-# Modifiers given through the !OPTIONS line apply to every test.
+LC_ALL=C cal 2001
 
+# Here tests with `w` count all occurrences, even when they are on the same line.
 
-LC_ALL=C cal 2001
+$ 7 months have 31 days
+w7: 31
 
+# Uppercase modifiers cancel previous modifiers
+
+$ 5 lines have a '31' day
+wW5: 31
 
-# Here tests with `w` count all occurrences, even when they are on the same line.
+
+# Modifiers given through the command line or through !OPTIONS apply to every test.
+
+!OPTIONS: --mod w
+LC_ALL=C cal 2001
 
 $ 7 months have 31 days
 7: 31
@@ -14,9 +23,5 @@ $ 7 months have 31 days
 $ 11 months have 30 days or more
 11: 30
 
-
-# Uppercase modifiers cancel previous modifiersrs.
-
-$ 5 lines have a '31' day
-W5: 31
-
+$ 7 months have a '31' day (W is here overriden by --mod w)
+W7: 31