Fix #1030: Disable AJAX Cach in Live Editor

Internet Explorer caches all AJAX get requests and decides when to expire
them in the cache. This commit disables caching on the GET request to
/data/<PAGE NAME>, which fixes IE displaying old page data when using the
live editor.

See http://www.dashbay.com/2011/05/internet-explorer-caches-ajax/ and
https://stackoverflow.com/questions/4303829/how-to-prevent-a-jquery-ajax-request-from-caching-in-internet-explorer

lib/gollum/public/gollum/livepreview/js/livepreview.js

@@ -394,6 +394,7 @@ var applyTimeout = function () {
     jQuery.ajax( {
       type: 'GET',
       url: baseUrl + '/data/' + path + key_no_leading_slash( 'page' ),
+      cache: false,
       success: function( data ) {
          editorSession.setValue( data );
       }