Resizes the map on tab change to fix issue #8

I don't think the code in the our thread at http://our.umbraco.org/projects/backoffice-extensions/google-maps-property-editor-w-google-places-autocomplete-lookup/bugs,-feedback-and-suggestions/53913-Fix-for-the-resize-bug works.

Problem is when the map is hidden when the page is initially loaded. Code listens for tab change and triggers a resize (as well as recentering to original position).