Make slug unique and fix the max_length.

taggit/models.py

@@ -6,7 +6,7 @@ from django.template.defaultfilters import slugify
 
 class Tag(models.Model):
     name = models.CharField(max_length=100)
-    slug = models.SlugField()
+    slug = models.SlugField(unique=True, max_length=100)
     
     def __unicode__(self):
         return self.name