Deployment improvements

[eixin]

Deployment improvements:

• specifying settings in base.yml
• create instagram.py and secret.py automatically
• perform syncdb and migrate automatically
• get the source code by revision (in setup_django_app.yml, might need to be changed onto particular branch (e.g. dev) )
• fix django.ini template, running uwsgi under an application user rather than www-data
• other miscellaneous fixes