indexing H5DataIO

[bendichter]

H5DataIO[slice] currently throws an error. I would like it instead to call H5DataIO.data[slice].

Motivations

1. This is clearly the intention.
2. It will help with tests. I am running into an issue with the unit tests when trying to implement Make all DynamicTables chunked and resizable by default #1067 the unit tests break because several of them try to index data without checking if it's an H5DataIO object. With the proposed change, we can simply say something like assert data_out[:] == data_in and this will work whether data_out is a list, h5py.Dataset, np.array, or H5DataIO object.

[oruebel]

This should be implemented in HDMF on the DataIO base class. The following PR on HDMF should fix this issue:

hdmf-dev/hdmf#141

[rly]

@bendichter I believe this has been resolved. Please close if so.