Switch our lazy array classes to use Dask instead?

@shoyer

In the long term, it would be nice to get ride of these uses of _data, maybe by switching entirely from our lazy array classes to Dask.

The subtleties of checking _data vs data are undesirable, e.g., consider the bug on these lines:

Lines 212 to 213 in 1a01208

    
           elif isinstance(var.data, dask_array_type): 
        
               values_str = short_dask_repr(var, show_dtype=False)

Provide feedback

	elif isinstance(var.data, dask_array_type):
	values_str = short_dask_repr(var, show_dtype=False)