maps external id's into sequential id's
Redis script for mapping external ID's to sequential ones. Adapted from crashlytics.
$ npm install redis-identity
Pass in a node-redis client, and an optional key to use for the id mappings.
var redis =client = redisidentity = client;;
The second argument is the optional for the mapping, it defaults to
var redis =client = redisidentity = client 'my-id-map';;