Support repeated executions of mocked requests
Support repeated executions of mocked requests

Currently, `aioresponses` does not support repeated execution
of the same mocked request which means you have to dupe the
mocked request in your code:

```python
with aioresponses() as mocked:
    mocked.get('http://auth')
    # some code that hits the above url
    mocked.get('http://auth')
    # some code that hits the above url for a second time
```

Fix is to add a `repeat` flag which allows the mock to be repeated:
```python
with aioresponses() as mocked:
    mocked.get('http://auth', repeat=True)
    # some code that hits the above url
    # some code that hits the above url for a second time
```

pnuckowski/aioresponses