Zarr open fails on ZipStore #141

In [1]: import zarr

In [2]: s = zarr.storage.ZipStore("reg_proj.zarr")

In [3]: z = zarr.open(s)
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-3-37024ca9ed12> in <module>()
----> 1 z = zarr.open(s)

/zopt/conda2/envs/nanshenv/lib/python2.7/site-packages/zarr/creation.pyc in open_array(store, mode, shape, chunks, dtype, compressor, fill_value, order, synchronizer, filters, cache_metadata, path, **kwargs)
    414     elif mode == 'a':
    415         if contains_group(store, path=path):
--> 416             err_contains_group(path)
    417         elif not contains_array(store, path=path):
    418             init_array(store, shape=shape, chunks=chunks, dtype=dtype,

/zopt/conda2/envs/nanshenv/lib/python2.7/site-packages/zarr/errors.pyc in err_contains_group(path)
     21 
     22 def err_contains_group(path):
---> 23     raise KeyError('path %r contains a group' % path)
     24 
     25 

KeyError: "path '' contains a group"