Like netCDF4.chartostring, but faster and more flexible.

def _numpy_char_to_bytes(arr):
    """Like netCDF4.chartostring, but faster and more flexible.
    """
    # based on: http://stackoverflow.com/a/10984878/809705
    arr = np.array(arr, copy=False, order='C')
    dtype = 'S' + str(arr.shape[-1])
    return arr.view(dtype).reshape(arr.shape[:-1])