use the app's view_functions dict to find the view to render

[rnagle]

I changed render_all to use a more reliable way of looking up view functions.

Essentially what this does is avoid a KeyError when using named endpoints. For example:

@app.route('/test/', endpoint='some-name')
def test_view():
    ...

Where endpoint differs from the view function name.

This works because app.app.view_functions is a dict with keys that correspond to the endpoint attribute of each of the app's routes.

Versus globals()[module].__dict__ which has keys for view function names only.

Works with every method of adding routes that I could think of.