Bump deepcopy from 0.6.3 to 2.1.0

Bumps [deepcopy](https://github.com/sasaplus1/deepcopy.js) from 0.6.3 to 2.1.0.
- [Changelog](https://github.com/sasaplus1/deepcopy.js/blob/master/HISTORY.md)
- [Commits](https://github.com/sasaplus1/deepcopy.js/compare/0.6.3...2.1.0)

---
updated-dependencies:
- dependency-name: deepcopy
  dependency-version: 2.1.0
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -54,7 +54,7 @@
     "browserify-istanbul": "^3.0.1",
     "chai": "^3.4.1",
     "deamdify": "^0.2.0",
-    "deepcopy": "^0.6.1",
+    "deepcopy": "^2.1.0",
     "del": "^2.0.2",
     "eslint": "^1.5.1",
     "eslint-config-pebble": "^1.2.0",