fetch default hook to include caching

lib/builder.js

@@ -176,26 +176,21 @@ Builder.prototype.reset = function(baseLoader) {
   loader.fetch = function(load) {
     var self = this;
     return Promise.resolve((builder.fetch || loaderFetch).call(this, load, function(load) {
-      return loaderFetch.call(self, load);
-    }))
-    .then(function(source) {
-      // custom fetch hook has to handle custom statting too
-      // by setting load.metadata.timestamp itself
-      if (builder.fetch)
-        return source;
-
-      // calling default fs.readFile fetch -> set timestamp as well for cache invalidation
-      return asp(fs.stat)(fromFileURL(load.address))
-      .then(function(stats) {
-        load.metadata.timestamp = stats.mtime.getTime();
-        return source;
-      }, function(err) {
-        // if the stat fails on a plugin, it may not be linked to the file itself
-        if (err.code == 'ENOENT' && load.metadata.loader)
+      return loaderFetch.call(self, load)
+      .then(function(source) {
+        // calling default fs.readFile fetch -> set timestamp as well for cache invalidation
+        return asp(fs.stat)(fromFileURL(load.address))
+        .then(function(stats) {
+          load.metadata.timestamp = stats.mtime.getTime();
           return source;
-        throw err;
-      });
-    })
+        }, function(err) {
+          // if the stat fails on a plugin, it may not be linked to the file itself
+          if (err.code == 'ENOENT' && load.metadata.loader)
+            return source;
+          throw err;
+        });
+      })
+    }))
     .then(function (source) {
       var metadata = load.metadata;
       if (metadata.sourceMap)