make taggit case insensitive
New tag instances arecreated for different input "rostock", "Rostock" and "ROSTOCK" and so on, but referring to the same. Check if can be made insensitive, e.g.: https://djangosnippets.org/snippets/305/
New tag instances arecreated for different input "rostock", "Rostock" and "ROSTOCK" and so on, but referring to the same. Check if can be made insensitive, e.g.: https://djangosnippets.org/snippets/305/