Remove import from the code in order to be able to minify the module

lib/caching.js

@@ -2,8 +2,12 @@
 /*jshint maxcomplexity:16*/
 var CallbackFiller = require('./callback_filler');
 var utils = require('./utils');
+var memory = require('./stores/memory.js');
+var none = require('./stores/none.js');
 var parseWrapArguments = utils.parseWrapArguments;
 
+var stores = {memory, none};
+
 /**
  * Generic caching interface that wraps any caching library with a compatible interface.
  *
@@ -25,7 +29,7 @@ var caching = function(args) {
         }
     } else {
         var storeName = args.store || 'memory';
-        self.store = require('./stores/' + storeName + '.js').create(args);
+        self.store = stores[storeName].create(args);
     }
 
     // do we handle a cache error the same as a cache miss?