NSRDB Intro notebook needs update

[stuchalk]

I am trying to run the Jupyter Notebook at https://github.com/NREL/hsds-examples/blob/master/notebooks/03_NSRDB_introduction.ipynb and it has errors:

• f.attrs['version'] should be f.attrs['Version'] (version is 3.0.6)
• running the following gives an error for meta = pd.DataFrame(f['meta'][...]) (see attached trackback file) nsrdb trackback.txt