Parse the json file and deserialize it into a struct

Parse the json file and deserialize it into a struct

Where the struct only has a 'name' field so far.

This commit shows a few new things in rust that we haven't seen
previously:

* The "mod config" to depend on a module contained in config.rs

* The ? operator ("try operator") which unwraps a Result if it is_ok,
  and insteadd returns an error if it is not.

* Dependencies on rust packages, (serde_json, and serde with the
  "derive" feature") used for the JSON parsing and deserializing.

* The derive attribute (spelled "#[derive(...)]" used to automatically
  create implementations of the Debug and Deserialize traits for our
  struct. Debug isn't used here, but could be used by passing a
  ConfigFile value to println! or format! macros using a "{:?}" format
  specifier.

* A closure accepting a single parameter: |e| { ... }