-------------------
Features added
^^^^^^^^^^^^^^
* Added new covalent radii: ``covalent_radius_bragg``,
``covalent_radius_slater``
* Added the ``c6`` dispersion coefficients
* Added ``gas_basicity``, ``proton_affinity`` and ``heat_of_formation``
* Added ``periodic_plot`` function for producing `bokeh <https://bokeh.org/>` based plots of the
periodic table
* Added ``jmol_color`` and ``cpk_color`` with different coloring schemes for
atoms
Bug fixes
^^^^^^^^^
* Changed the series of elements 113, 114, 115, 116 to poor metals