Default to https for the CORS API.

Heroku uses Strict Transport Security (HSTS), which forces that all
requests to *.herokuapp.com must use HSTS. However. Chrome cannot read
the CORS response after a HSTS redirect due to https://crbug.com/387198.

Since the request is going to be redirected to https anyway, the demo
and the documentation will use https by default.
0.2.2 - Expose every response header #12
ability to use proxy handler in independent way