Use mapconfig-extension from windshaft

npm-shrinkwrap.json

@@ -533,7 +533,7 @@
                 },
                 "inherits": {
                   "version": "2.0.1",
-                  "from": "inherits@~2.0.1",
+                  "from": "inherits@2",
                   "resolved": "https://registry.npmjs.org/inherits/-/inherits-2.0.1.tgz"
                 },
                 "isarray": {
@@ -828,8 +828,8 @@
     },
     "windshaft": {
       "version": "1.5.1",
-      "from": "https://github.com/CartoDB/Windshaft/tarball/mapconfig-extension-histogram",
-      "resolved": "https://github.com/CartoDB/Windshaft/tarball/mapconfig-extension-histogram",
+      "from": "https://github.com/CartoDB/Windshaft/tarball/mapconfig-extension",
+      "resolved": "https://github.com/CartoDB/Windshaft/tarball/mapconfig-extension",
       "dependencies": {
         "mapnik": {
           "version": "1.4.15-cdb5",

package.json

@@ -29,7 +29,7 @@
         "node-statsd": "~0.0.7",
         "underscore"  : "~1.6.0",
         "dot": "~1.0.2",
-        "windshaft": "https://github.com/CartoDB/Windshaft/tarball/mapconfig-extension-histogram",
+        "windshaft": "https://github.com/CartoDB/Windshaft/tarball/mapconfig-extension",
         "step": "~0.0.6",
         "queue-async": "~1.0.7",
         "request": "~2.62.0",