testing fixtures

Need to create a system where the users can add data to a fixture that can be used in the testing of their app.
`this` will refer to different things, depending on how this function was called:
```javascript
console.log(LocationState.testing() === LocationState);

var testing = LocationState.testing;
console.log(testing() === global);

var foo = {};
foo.testing = testing;
console.log(foo.testing() === foo);
```

We will need to create our own context, something like:

```javascript
var self = {};

self.add_location = add_location;
...

return self;
```