Pygauss

- Added zero-point energy recovery :py:func:`pygauss.molecule.Molecule.get_zeropt_energy` and ability to correct in :py:func:`pygauss.molecule.Molecule.get_opt_energy`
- Added HOMO-LUMO overlay option in :py:func:`pygauss.molecule.Molecule.plot_dos` to visualise and assess band-gaps
- Added top-level functions for saving/loading objects (Molecule, Analysis) to a file; :py:func:`pygauss.save_object` and :py:func:`pygauss.load_object`
- other minor fixes

Improved the :py:class:`pygauss.docs.MSDocument` class:
- Improved :py:func:`pygauss.docs.MSDocument.add_markdown` to handle more markdown syntax
- Added :py:func:`pygauss.docs.MSDocument.add_docstring` to add multiple paragraphs (with markdown)
- Improved :py:func:`pygauss.docs.MSDocument.add_dataframe` and :py:func:`pygauss.docs.MSDocument.add_mpl`
- there is now a caption option with built-in figure/table number count

- Density of States (DoS) and Partial Density of States (PDoS) analysis capabilities added.
- Addition of :py:func:`pygauss.analysis.Analysis.plot_mol_graphs` for data comparison
- :py:func:`pygauss.analysis.Analysis.add_runs` method now utilises the :py:mod:`multiprocessing` module for faster data input*
- Improvement of API documentation

**Back-compatibility note**: replaced `plot_optimisation_E` and `get_optimisation_E` with
:py:func:`pygauss.molecule.Molecule.get_opt_energy` and :py:func:`pygauss.molecule.Molecule.plot_opt_energy`,
to adhere with standard naming conventions.

*multiprocessing not currently available in Windows or over SSH

- added the :py:mod:`pygauss.docs` module for outputting analysis to documents
- initially utilising the :py:class:`docx.document.Document` within :py:class:`pygauss.docs.MSDocument`

Addition of continuous integrated testing using [Travis](https://travis-ci.org/) and testing coverage analysis using [Coverall](https://coveralls.io/).

addition of Sphinx documentation