add proper db indexes

[harmv]

django-email-confirmation misses some obvious database indexes

We found this issue when using email-confirmation on really large databases.

2 issues found:
EmailConfirmation.confirmation_key <- you always do a lookup with confirmation_key as key
EmailAddress.email <- when looking for dups etc, you query on this key

patch below:

Index: 3rdparty/django-email-confirmation/emailconfirmation/models.py
===================================================================
--- 3rdparty/django-email-confirmation/emailconfirmation/models.py      (revision 417)
+++ 3rdparty/django-email-confirmation/emailconfirmation/models.py      (working copy)
@@ -44,7 +44,7 @@
 class EmailAddress(models.Model):

     user = models.ForeignKey(User)
-    email = models.EmailField()
+    email = models.EmailField(db_index=True)
     verified = models.BooleanField(default=False)
     primary = models.BooleanField(default=False)

@@ -135,7 +135,7 @@

     email_address = models.ForeignKey(EmailAddress)
     sent = models.DateTimeField()
-    confirmation_key = models.CharField(max_length=40)
+    confirmation_key = models.CharField(max_length=40,db_index=True)

     objects = EmailConfirmationManager()