Added field and award logic to allow a minimum number of pre-requisites to be specified - this allows a badge to be automatically awarded when (for example) 3 out of the chosen 5 prerequisites have been obtained.
Added field and logic to have a 'badge awarding badge.'
A badge is optionally added to the new allows_awarding_badge field. When a user has the badge referenced in the this field, they are allowed to award the current badge
Better support for django 1.5 custom user models: rather than importing User from django.contrib.auth.models, first try to get the user model using get_user_model()
Revert to using AUTH_USER_MODEL from settings in place of actual model; this breaks one query.