Test failures with numpy 1.14.0

```
________________________________ test_validate _________________________________

def test_validate():
assert validate(int, 1)
> assert validate('int', 1)
E AssertionError: assert False
E + where False = validate('int', 1)

datashape/tests/test_user.py:8: AssertionError
___________________________ test_nested_iteratables ____________________________

def test_nested_iteratables():
> assert validate('2 * 3 * int', [(1, 2, 3), (4, 5, 6)])
E AssertionError: assert False
E + where False = validate('2 * 3 * int', [(1, 2, 3), (4, 5, 6)])

datashape/tests/test_user.py:19: AssertionError
_____________________________ test_validate_dicts ______________________________

def test_validate_dicts():
> assert validate('{x: int, y: int}', {'x': 1, 'y': 2})
E AssertionError: assert False
E + where False = validate('{x: int, y: int}', {'x': 1, 'y': 2})

datashape/tests/test_user.py:26: AssertionError
________________________ test_tuples_can_be_records_too ________________________

def test_tuples_can_be_records_too():
> assert validate('{x: int, y: real}', (1, 2.0))
E AssertionError: assert False
E + where False = validate('{x: int, y: real}', (1, 2.0))

datashape/tests/test_user.py:36: AssertionError
```

- datashape 0.5.4
- Python 2.7 and 3.6