Do not show the comments field in OfferSubscritionInline from the Member admin view

Related to issue#105.

coin/members/admin.py

@@ -35,6 +35,7 @@ class MembershipFeeInline(admin.TabularInline):
 class OfferSubscriptionInline(admin.TabularInline):
     model = OfferSubscription
     extra = 0
+    exclude = ('comments',)
     readonly_fields = ('get_subscription_reference', 'subscription_date', 'resign_date',
                        'commitment', 'offer', 'show_change_link')