* NEW: Updated dependencies
* NEW: Added basic integration test and fixture
* NEW: Separated the main application's logic (zeps-core) to a library
  project (zeps)
* NEW: Added config::read_world() method.
* NEW: Added data::World::stations() and data::Network::stations()
  methods, which return optimized iterators.
* BUG: Coordinates are now signed integers

* NEW: Renamed the World structures to Universe
* NEW: Add some public methods so the compiler won't complain about
  unused fields
* NEW: Added error management (using the failure crate)
* NEW: Added configuration errors
* NEW: Added missing NetworkConnection structure
* NEW: Added Station.is_hidden field

* NEW: lines are now imported and validated (e.g. for valid stations in them).
* NEW: instead of a HashMap<String, Station>, stations of a network are now in a HashMap<String, Rc<Station>>.
* NEW: updated fixture to validate.

* NEW: the `subname` key in the stations objects is now `sub_name`.

* NEW: network explicit connections (in networks_connections.connections) are loaded and the stations are checked in their respective networks.

What could be improved:
- error message on unknown station, to specify the context and the network.

* NEW: added tests to check if the universes are correctly loaded and parsed, and to check if errors are correctly handled.

* OPT: made a condition more “rustic”.