Enabled build on windows to succeed

Author: k2snowman69

package-lock.json

@@ -9,7 +9,7 @@
     "url": "git://github.com/CassetteRocks/react-infinite-scroller.git"
   },
   "scripts": {
-    "build": "mkdir -p dist && babel src/InfiniteScroll.js --out-file dist/InfiniteScroll.js",
+    "build": "mkdirp dist && babel src/InfiniteScroll.js --out-file dist/InfiniteScroll.js",
     "prepublish": "npm run build",
     "test": "nyc npm run spec",
     "spec": "_mocha -R spec ./test/test_helper.js --recursive test/*_test.js",
@@ -33,6 +33,7 @@
     "url": "https://github.com/CassetteRocks/react-infinite-scroller/issues"
   },
   "dependencies": {
+    "mkdirp": "^0.5.1",
     "prop-types": "^15.5.8"
   },
   "peerDependencies": {
@@ -72,4 +73,4 @@
     "sinon": "^2.1.0",
     "webpack": "^2.5.1"
   }
-}
+}