Added urls to newsletter access
Added new views to get and send newsletter
Added NewsletterManager to Newsletter model
Adding new newsletter views
Merge branch 'update_newsletter_models' of github.com:python-spain/pycones-web into update_newsletter_models
Added Subscription model to administrator
Updated Newsletter unicode method and added to Subscription model
Added access to last newsletter
Added new views get_last_newsletter and get_newsletter
Fixed get_newsletter and send_newsletter urls
New template to view newsletter details