Fix Barometer on SSL websites.

[ollieza]

1. Change all links to SSL, currently errors get an error: BAROMETER is undefined.
2. http://getbarometer.s3.amazonaws.com/assets/barometer/images/transparent.gif - change to SSL.

[neilsh]

Would it be feasible for barometer to use protocol-relative URLs throughout the codebase to support both HTTP and HTTPS?

[alexlehm]

I have noticed this issue now as well since I have switched my page to ssl.
the local script can be changed to https by using //hostname/path instead of http, for the bits in the javascript code itself, I assume evaluating location.protocol would be the easiest way, for the images relative paths are also possible (I assume)