Added json api

Resolves #6 
Something like:

```json
[
    {
        "_id": "548a1687986431a1c776834c",
        "name": "say-hello",
        "type": "single",
        "data": null,
        "priority": 0,
        "repeatInterval": "10 seconds",
        "lastModifiedBy": null,
        "nextRunAt": "2014-12-17T20:27:28.167Z",
        "lockedAt": null,
        "lastRunAt": "2014-12-17T20:27:18.167Z",
        "lastFinishedAt": "2014-12-17T20:27:18.168Z"
    },
    {
        "_id": "548a1687986431a1c776834d",
        "name": "here is a task",
        "type": "single",
        "data": null,
        "priority": 10,
        "repeatInterval": "30 seconds",
        "lastModifiedBy": null,
        "nextRunAt": "2014-12-17T20:27:38.164Z",
        "lockedAt": null,
        "lastRunAt": "2014-12-17T20:27:08.164Z",
        "lastFinishedAt": "2014-12-17T20:27:08.166Z",
        "failReason": "Cannot read property 'type' of null",
        "failedAt": "2014-12-17T20:27:08.166Z"
    },
    {
        "_id": "5491db1d650cecb7f036e1b1",
        "name": "something",
        "type": "single",
        "data": {
            "type": "ice cream"
        },
        "priority": 0,
        "repeatInterval": "45 seconds",
        "lastModifiedBy": null,
        "nextRunAt": "2014-12-17T19:35:57.536Z",
        "lockedAt": "2014-12-17T19:35:57.541Z"
    }
]
```

It's all the data agenda will give us.