fix(package): downgrade source-map v0.7.0...0.5.6 (#309)

Author: hackeryarn

package.json

@@ -31,7 +31,7 @@
     "async": "^2.0.0",
     "loader-utils": "^1.0.0",
     "lodash": "^4.0.0",
-    "source-map": "^0.7.0",
+    "source-map": "^0.5.6",
     "webpack-dev-middleware": "^1.12.0"
   },
   "devDependencies": {