Add support for `array.array`

```
>>> import array, jsonplus
>>> array.array('f', [1.1, 2.2])
array('f', [1.100000023841858, 2.200000047683716])
>>> jsonplus.dumps(array.array('f', [1.1, 2.2]))
...
TypeError: array('f', [1.100000023841858, 2.200000047683716]) is not JSON serializable
```