add citation notice, cclib 1.6 compatibility

New features in web interface

ESIgen v0.0.4 offers new additions in the web interface, namely
more options for downloading and exporting reports. Everything
is summarized in the newly available documentation at
esigen.readthedocs.io

TLDR: Download XYZ, CML, JSON, CJSON and export to Github Gist,
Zenodo and Fishare. PDF is now discouraged in honor of science
reproducibility.

New fields for Gaussian & ChemShell

- Support for ModRedundant Scans (Gaussian only)
- Experimental support for some ChemShell QM/MM jobs
- New NGL version, which add supports for interactive measurements
- New `checks.md` template for daily analysis tasks

Unit consistency for thermochemistry

Pre-alpha public release