Upgrade lodash to latest

Author: simonsmith

package.json

@@ -17,8 +17,8 @@
     "commander": "~2.9.0",
     "cssnano": "^3.3.2",
     "fs-extra": "^0.26.2",
-    "lodash.difference": "^3.2.2",
-    "lodash.isempty": "^3.0.4",
+    "lodash.difference": "^4.0.2",
+    "lodash.isempty": "^4.1.1",
     "object-assign-deep": "0.0.4",
     "pad-component": "0.0.1",
     "postcss": "^5.0.12",