dashboard: make gravatar profile image default

circle/dashboard/models.py

@@ -86,7 +86,7 @@ class Profile(Model):
         help_text=_('Unique identifier of the person, e.g. a student number.'))
     instance_limit = IntegerField(default=5)
     use_gravatar = BooleanField(
-        verbose_name=_("Use Gravatar"), default=False,
+        verbose_name=_("Use Gravatar"), default=True,
         help_text=_("Whether to use email address as Gravatar profile image"))
     email_notifications = BooleanField(
         verbose_name=_("Email notifications"), default=True,