Add meal index endpoint

As a user,

I should be able to request a list of all meals within the system by submitting a GET request to the endpoint '/api/v1/meals'.

The application should return a 200 status, along with an array of meal items and the foods contained within them, formatted similar to the following:
```
[
{
"id": 1,
"name": "Breakfast",
"foods": [
{
"id": 1,
"name": "Banana",
"calories": 150
},
{
"id": 6,
"name": "Yogurt",
"calories": 550
},
{
"id": 12,
"name": "Apple",
"calories": 220
}
]
},
{
"id": 2,
"name": "Snack",
"foods": [
{
"id": 1,
"name": "Banana",
"calories": 150
},
{
"id": 9,
"name": "Gum",
"calories": 50
},
{
"id": 10,
"name": "Cheese",
"calories": 400
}
]
},
{
"id": 3,
"name": "Lunch",
"foods": [
{
"id": 2,
"name": "Bagel Bites - Four Cheese",
"calories": 650
},
{
"id": 3,
"name": "Chicken Burrito",
"calories": 800
},
{
"id": 12,
"name": "Apple",
"calories": 220
}
]
},
{
"id": 4,
"name": "Dinner",
"foods": [
{
"id": 1,
"name": "Banana",
"calories": 150
},
{
"id": 2,
"name": "Bagel Bites - Four Cheese",
"calories": 650
},
{
"id": 3,
"name": "Chicken Burrito",
"calories": 800
}
]
}
]
```

- [x] Tested
- [x] Documented