Fix problem with iframe and HTTP and HTTPS

In a page loaded with HTTPS is insecure to load a iframe with
HTTP and most of the browsers will block it. [1]

To avoid this problem we could let the browser use the currently
protocol. [2]

[1] https://support.mozilla.org/en-US/questions/958305#answer-476475
[2] http://stackoverflow.com/q/9161769/1802726
Merge pull request #483 from r-gaia-cs/https

Fix problem with iframe and HTTP and HTTPS