More robust reading of schema files

In the [day-of-datomic](https://github.com/Datomic/day-of-datomic) they use `datomic.Util/readAll` [here](https://github.com/Datomic/day-of-datomic/blob/master/src/datomic/samples/io.clj#L18) to read EDN files -- this has the added benefit of allowing multiple EDN vectors within the same file to be read. This PR adds that functionality.