Make cache-busting optional

Closes #70

lib/proto/parse-options.js

@@ -19,6 +19,7 @@ module.exports = function(options){
     }
   }
   this.options.scrollTo = (typeof this.options.scrollTo === 'undefined') ? 0 : this.options.scrollTo;
+  this.options.cacheBust = (typeof this.options.cacheBust === 'undefined') ? true : this.options.cacheBust
   this.options.debug = this.options.debug || false
 
   // we can’t replace body.outerHTML or head.outerHTML