EventsClient fix - ids are string, not ints

The ids for the entities in an event are ints, but the id of the event itself is not:

```
[
  {
    "type": "Event",
    "public": true,
    "payload": {
    },
    "repo": {
      "id": 3,
      "name": "octocat/Hello-World",
      "url": "https://api.github.com/repos/octocat/Hello-World"
    },
    "actor": {
      "id": 1,
      "login": "octocat",
      "gravatar_id": "somehexcode",
      "avatar_url": "https://github.com/images/error/octocat_happy.gif",
      "url": "https://api.github.com/users/octocat"
    },
    "org": {
      "id": 1,
      "login": "github",
      "gravatar_id": "somehexcode",
      "url": "https://api.github.com/orgs/github",
      "avatar_url": "https://github.com/images/error/octocat_happy.gif"
    },
    "created_at": "2011-09-06T17:26:27Z",
    "id": "12345"
  }
]
```

Resolves #263