Utility functions for printing version information

[andersy005]

It would be nice to have an esmlab.show_versions() similar to xarray's xr.show_versions().

See:

• https://github.com/pydata/xarray/blob/master/xarray/util/print_versions.py
• https://github.com/pandas-dev/pandas/blob/master/pandas/util/_print_versions.py