NilCache returns a struct satisfying the Cache interface that goes nowhere
and does nothing. All calls will GNDN, and Get will always result in a cache
miss. This option should probably not be used except for writing this
package's tests.
RedisCache returns a new evego.Cache object that uses a Redis backend.
It takes a server hostname/port in the format accepted by net.Dial and,
optionally, a password as parameters.