Fixed #43 -- Made tag names unique.

CHANGES.rst

 Version 0.10 (unreleased)
 -------------------------
 
+* Tag names are unique now, use the provided South migrations to upgrade.
+
 Version 0.9.3
 -------------
 

taggit/migrations/0002_unique_tagnames.py

+# -*- coding: utf-8 -*-
+import datetime
+from south.db import db
+from south.v2 import SchemaMigration
+from django.db import models
+
+
+class Migration(SchemaMigration):
+
+    def forwards(self, orm):
+        # Adding unique constraint on 'Tag', fields ['name']
+        db.create_unique(u'taggit_tag', ['name'])
+
+
+    def backwards(self, orm):
+        # Removing unique constraint on 'Tag', fields ['name']
+        db.delete_unique(u'taggit_tag', ['name'])
+
+
+    models = {
+        u'contenttypes.contenttype': {
+            'Meta': {'ordering': "('name',)", 'unique_together': "(('app_label', 'model'),)", 'object_name': 'ContentType', 'db_table': "'django_content_type'"},
+            'app_label': ('django.db.models.fields.CharField', [], {'max_length': '100'}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'model': ('django.db.models.fields.CharField', [], {'max_length': '100'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '100'})
+        },
+        u'taggit.tag': {
+            'Meta': {'object_name': 'Tag'},
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '100'}),
+            'slug': ('django.db.models.fields.SlugField', [], {'unique': 'True', 'max_length': '100'})
+        },
+        u'taggit.taggeditem': {
+            'Meta': {'object_name': 'TaggedItem'},
+            'content_type': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "u'taggit_taggeditem_tagged_items'", 'to': u"orm['contenttypes.ContentType']"}),
+            u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'object_id': ('django.db.models.fields.IntegerField', [], {'db_index': 'True'}),
+            'tag': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "u'taggit_taggeditem_items'", 'to': u"orm['taggit.Tag']"})
+        }
+    }
+
+    complete_apps = ['taggit']
\ No newline at end of file

taggit/models.py

@@ -7,7 +7,7 @@ from django.utils.translation import ugettext_lazy as _, ugettext
 
 
 class TagBase(models.Model):
-    name = models.CharField(verbose_name=_('Name'), max_length=100)
+    name = models.CharField(verbose_name=_('Name'), unique=True, max_length=100)
     slug = models.SlugField(verbose_name=_('Slug'), unique=True, max_length=100)
 
     def __unicode__(self):