anchor.diff:  experimentation.  So from the root directory, fire up a repl and start
   experimenting:
   
  -```clojure
  +[[app-listing]]
  +[source,clojure]
  +----
   $ lein repl
   nREPL server started on port 52304 on host 127.0.0.1 - nrepl://127.0.0.1:52304
   REPL-y 0.3.5, nREPL 0.2.6
  
positive.code: ### field types
  
  The value part of an entity-map is just a map.  The datastore
  restricts the permissible value types; see  [Properties and value types](https://cloud.google.com/appengine/docs/java/datastore/entities#Java_Properties_and_value_types)
  
  ```
  (entity-map [:Foo/Bar] {:a 1})  ;; java.lang.Long
  
negative.code: 
  ## testing
  
  See the link:test/clojure/migae[tests] for lots of examples of how to use
  the library.  Be **be forewarned**, the test cases are in flux; some
  of them are outdated, and the api is changing.
  
  ## types
  
  * `migae.datastore.PersistentEntityMap` - migae representation of underlying `com.google.appengine.api.datastore.Entity`.  Implements IPersistentCollection, IPersistentMap, IMapEntry, etc.  See link:doc/Entities.md[Entities].
  * `migae.datastore.Keychain`  - migae representation of underlying `com.google.appengine.api.datastore.Key`.  A vector of Clojure keywords.  See link:doc/Keychains.md[Keychains].  (**Not yet implemented**)
  
  These are represented in migae as `entity-map` and `keychain`, respectively.
  
  