Document options loaded from app.config in init_app

[nomorepanic]

The init_app function loads some options from app.config, I think this should be added to the docs, as it provides a mean of configuration.

self._csrf_name = app.config.get('CSRF_COOKIE_NAME', '_csrf_token')
self._csrf_header_name = app.config.get('CSRF_HEADER_NAME',
                                                'X-CSRFToken')
self._csrf_disable = app.config.get('CSRF_DISABLE',
                                            app.config.get('TESTING', False))
self._csrf_timeout = app.config.get('CSRF_COOKIE_TIMEOUT',
                                            timedelta(days=5))
self._csrf_secure = app.config.get('CSRF_COOKIE_SECURE', False)
self._csrf_httponly = app.config.get('CSRF_COOKIE_HTTPONLY', False)
self._type = app.config.get('SEASURF_INCLUDE_OR_EXEMPT_VIEWS',
                                    'exempt')

Especially CSRF_COOKIE_NAME which can be set to 'csrf_token' to get compatibility with Flask-Admin.

[maxcountryman]

I'm fine with adding more documentation.

[killthekitten]

Addressed in #104, but maybe needs a release? The website wasn't updated @maxcountryman