backends: Backends are the glue that store the minimodel
Add tests for Minimodel with multiple managers
Add minimodels configuration

minimodels will search for two configuration methods:

    - django's settings MINIMODELS variable
        MINIMODELS = {
            'last' : {
                'host': 'localhost',
                'db': 0,
                'port': 6379,
                'backend': 'RedisBackend',
            },
            'history': {
                'host': 'localhost',
                'protocol': 'http',
                'port': 9200,
                'backend': 'ElasticSearchBackend',
            }
        }

    A yaml configuration file specified in a the MINIMODEL_CONF
environment variable:

    history:
        host: localhost
        port: 9200
        protocol: http
        backend: ElasticSearchBackend

    last:
        host: localhost
        port: 6379
        db: 0
        backend: RedisBackend
Add minimodels specific exceptions