allow for configuration to override the favicon

Closes #5

tests/test_factory.py

@@ -58,3 +58,13 @@ def test_media_file_access(client):
     response = client.get('/media/favicon.png')
     assert response.status_code == 200
     assert response.headers['content-type'] == 'image/png'
+
+
+def test_favicon_override():
+    """Test that a configuration with a specific favicon overrides the default."""
+    instance_path = os.path.join(HERE, 'instance')
+    app = create_app(instance_path=instance_path, test_config={'FAVICON': '/media/foo.png'})
+    client = app.test_client()
+    response = client.get('/no-title')
+    assert response.status_code == 200
+    assert b'<link rel="icon" href="/media/foo.png">' in response.data