Add tests for portfolio funding route

This adds a helper to grab a template's context. Using a helper from the
Flask documentation: http://flask.pocoo.org/docs/1.0/signals/?highlight=template_rendered#subscribing-to-signals

Pipfile

@@ -38,6 +38,7 @@ pytest-env = "*"
 pytest-cov = "*"
 selenium = "*"
 honcho = "*"
+blinker = "*"
 
 [requires]
 python_version = "3.6.6"