add npmrc

.npmrc

@@ -0,0 +1,4 @@
+phantomjs_cdnurl=https://npm.taobao.org/mirrors/phantomjs/
+chromedriver_cdnurl=https://npm.taobao.org/mirrors/chromedriver/
+sass_binary_site=https://npm.taobao.org/mirrors/node-sass/
+electron_mirror=https://npm.taobao.org/mirrors/electron/