Bump Chrome shell to 2.1.6

Author: gaearon

shells/chrome/manifest.json

@@ -2,7 +2,7 @@
  "manifest_version": 2,
  "name": "React Developer Tools",
  "description": "Adds React debugging tools to the Chrome Developer Tools.",
- "version": "2.1.5",
+ "version": "2.1.6",
  "minimum_chrome_version": "43",
  "icons": {
  "16": "icons/16-production.png",