Modify JS to support HTTPS

[GoogleCodeExporter]

This is a really simple fix, but in the code, there's a line that's loading the 
MarkerClusterer images over http:

/**
 * The marker cluster image path.
 *
 * @type {string}
 * @private
 */
MarkerClusterer.prototype.MARKER_CLUSTER_IMAGE_PATH_ =
    'http://google-maps-utility-library-v3.googlecode.com/svn/trunk/markerclusterer/' +
    'images/m';

if we just change that to:

/**
 * The marker cluster image path.
 *
 * @type {string}
 * @private
 */
MarkerClusterer.prototype.MARKER_CLUSTER_IMAGE_PATH_ =
    '//google-maps-utility-library-v3.googlecode.com/svn/trunk/markerclusterer/' +
    'images/m';

...it'll work without throwing any error messages about loading over http 
instead of https!

Original issue reported on code.google.com by [email protected] on 5 Dec 2013 at 3:25