[#908] Removed old reference to boolean and an old todo for checkboxes

plugins/documentcloud/popcorn.documentcloud.js

@@ -68,10 +68,9 @@ api - https://github.com/documentcloud/document-viewer/blob/master/public/javasc
         },
         preload: {
           elem: "input",
-          type: "boolean",
+          type: "checkbox",
           label: "Preload",
-          default: true,
-          optional: true
+          default: true
         },
         page: {
           elem: "input",

plugins/mustache/popcorn.mustache.js

@@ -198,7 +198,6 @@
         type: "text",
         label: "Data"
       },
-      /* TODO: how to show a checkbox/boolean? */
       dynamic: {
         elem: "input",
         type: "checkbox",