fix use np.array.all() instead of Python all()

[pablogventura]

Fix this error using Numpy when i call to is_constant in deutsch jozsa:

`/usr/local/lib/python2.7/dist-packages/grove/deutsch_jozsa/deutsch_jozsa.pyc in is_constant(self, cxn, bitstring_map)
57 # We are only running a single shot, so we are only interested in the first element.
58 bitstring = np.array(returned_bitstring, dtype=int)
---> 59 constant = all([bit == 0 for bit in bitstring])
60 return constant
61

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
`

Now it uses all function from Numpy instead of builtin all function.