include all slots in schedule json

This changes the schedule json feed so that it returns all slots rather than only certain types of released presentations and lightning talks.

I haven't tested this against real pyohio data, but I did run it against the data I have from another conference, and I also created some dummy objects locally. You can see the example output below.



```
[
    {
        "description": "",
        "tags": "",
        "abstract": "",
        "conf_key": 1,
        "released": true,
        "authors": null,
        "duration": 60,
        "room": "Tutorial Room",
        "kind": "tutorial_break",
        "end": "2014-07-26T09:00:00",
        "name": "Breakfast",
        "license": "",
        "conf_url": null,
        "start": "2014-07-26T08:00:00",
        "contact": null
    },
    {
        "description": "",
        "tags": "",
        "abstract": "",
        "conf_key": 3,
        "released": true,
        "authors": null,
        "duration": 60,
        "room": "Cartoon 1",
        "kind": "break",
        "end": "2014-07-26T09:00:00",
        "name": "talk breakfast",
        "license": "",
        "conf_url": null,
        "start": "2014-07-26T08:00:00",
        "contact": null
    },
    {
        "description": "Nam ullamcorper ante a velit volutpa",
        "tags": "",
        "abstract": "Sed elit urna, fringilla ac sem ac, vehicula viverra dolor. Mauris luctus ligula vel ligula facilisis, ut scelerisque urna ullamcorper. Curabitur in eleifend ligula, eget pharetra lacus. Praesent feugiat hendrerit laoreet. Aliquam sit amet imperdiet lorem. Fusce pretium, mi non dignissim sagittis, libero tortor sodales magna, ac blandit odio ipsum quis purus? Curabitur tincidunt vitae tortor amet.\r\n",
        "conf_key": 2,
        "released": true,
        "authors": [
            "Foo Bar"
        ],
        "duration": 60,
        "room": "Cartoon 2",
        "kind": "tutorial",
        "end": "2014-07-26T10:00:00",
        "name": "A tutorial",
        "license": "",
        "conf_url": "https://localhost/schedule/presentation/1/",
        "start": "2014-07-26T09:00:00",
        "contact": [
            "shekay@pobox.com"
        ]
    },
    {
        "description": "Description",
        "tags": "",
        "abstract": "Suspendisse eget dui eget nibh vulputate tristique. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Pellentesque a neque magna. Duis hendrerit semper eleifend. Praesent ullamcorper elit a magna feugiat, at tincidunt est blandit. Nulla facilisi. Duis eu ultricies nisl, scelerisque bibendum nisi. Duis euismod consectetur iaculis. Cum sociis natoque penatibus id.\r\n",
        "conf_key": 4,
        "released": false,
        "authors": [
            "Foo Bar"
        ],
        "duration": 60,
        "room": "Barbie",
        "kind": "talk",
        "end": "2014-07-26T10:00:00",
        "name": "A talk",
        "license": "",
        "conf_url": "https://localhost/schedule/presentation/2/",
        "start": "2014-07-26T09:00:00",
        "contact": [
            "shekay@pobox.com"
        ]
    }
]
```