Add settings model (#54)

* Adds a basic settings model

* Added more settings methods; Hooked up initial settings runner to app boot

* Update onboarding flow to use settings model instead of session data

test/pinchflat/startup_tasks_test.exs

@@ -0,0 +1,16 @@
+defmodule Pinchflat.StartupTasksTest do
+  use Pinchflat.DataCase
+
+  alias Pinchflat.Settings
+
+  # Since this runs on app boot (even in the test env),
+  # any actions in the `init/1` function will already have
+  # run. So we can only test the side effects of those actions,
+  # rather than the actions themselves.
+
+  describe "apply_default_settings" do
+    test "sets default settings" do
+      assert Settings.get!(:onboarding) == true
+    end
+  end
+end