Add save and load model options.
Add save and load UI buttons.
Stop storing data and updating it. Instead just query every time we need data.
Merge branch 'master' into save_load
Add tests for PI Configuration model.
Fix issue deleting observer.
Add test for ruby_pi app.
Revert "Add test for ruby_pi app." to fix issues with rake test.

This reverts commit 2e02ed37fa6eb2f2aadffb5d98e66fe41b03963d.
Add blank suite for upcoming view tests.
Move save and load from yaml to PIConfiguration class methods.
Begin requiring views to respond to stop_observing_model and start_observing_model methods.
Begin testing views.
Add test for system stats widget.
Add tests for building count table.
Fix issue where building count table did not require gtk3.
Add tests for buildings_list_store.
Add test cases for planet widgets.
Add test case for EditExtractorWidget.
Add test cases for EditFactoryWidget.
Add basic test cases for building view widget. These will probably need to be refined in the future.
Add TODO comment.
Add test case for building image.
Have the main app tell the widget it can observe when it creates it.
Set up a name for the YAML filter.
Force files to be saved as .yml.
Confirm if the user tries to overwrite a file that already exists.