add test to ensure that server supports datetimes

@hhuuggoo I think that the server already supports datetimes.  

I recommend using DyND to launder the resulting json coming from the server with the datashape that is also shipped as in this test.

```python
data = json.loads(response.data)
result = nd.array(data['data'], type=data['datashape'])
result = into(whatever, result)
```