Readme: Update suggested bundler gem version
Add More Detail to Error Messages

* This adds the new error message fields `error_user_message` and `error_user_title` which contain valuable failure information
* https://developers.facebook.com/docs/graph-api/using-graph-api/v2.1

**Example**
``` json
  {
    "error": {
      "message": "Message describing the error",
        "type": "OAuthException",
        "code": 190,
        "error_subcode": 460,
        "error_user_title": "A title",
        "error_user_msg": "A message"
    }
  }
```
Merge pull request #412 from richrines/rr-jk-better-error-messages

Add More Detail to Error Messages
Merge pull request #403 from thomasklemm/patch-1

Readme: Update suggested bundler gem version