fix(package): update deepcopy to version 2.0.0

Closes #7

Author: greenkeeper[bot]

package.json

@@ -27,7 +27,7 @@
   ],
   "license": "MIT",
   "dependencies": {
-    "deepcopy": "^0.6.3",
+    "deepcopy": "^2.0.0",
     "tosource": "^1.0.0"
   },
   "devDependencies": {