Add optional categories of day1_am, day1_pm, day2_am, and day2_pm

Prior to this change, running the check.py helper would list the categories above as superfluous. Since these categories are in the default index.html page, it makes sense to include them as optional rather than listing them as superfluous.

tools/check.py

@@ -338,7 +338,11 @@ def check_pass(value):
     'eventbrite': (False, check_eventbrite, 'Eventbrite key appears invalid.'),
     'etherpad':   (False, check_etherpad, 'Etherpad URL appears invalid.'),
     'venue':      (False, check_pass, 'venue name not specified'),
-    'address':    (False, check_pass, 'address not specified')
+    'address':    (False, check_pass, 'address not specified'),
+    'day1_am':    (False, check_pass, 'day1_am not specified'),
+    'day1_pm':    (False, check_pass, 'day1_pm not specified'),
+    'day2_am':    (False, check_pass, 'day2_am not specified'),
+    'day2_pm':    (False, check_pass, 'day2_pm not specified')
 }
 
 # REQUIRED is all required categories.