~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Validation: required metatags are initialized to empty string raise
exception ``ValueError``
* Hard refactor of ``Meta`` class
* Metainformation tags languages no longer hardcoded, only English, but
ready to increase the comparison sets with all the tags; maybe in the
future a JSON file will all translations will be used
* Update user documentation
* Refactor ``cli.py`` moving the ``main`` entry to ``main.py``
* Refactor ``Builder`` reducing redundant code
* ``Meta`` class now raises exceptions if meta data is invalid or
insufficient; validation of titles (always) and dates (if required)
* Array manipulation functions in ``dataman.py`` file
* Update dependency versions in ``setup.py``
* Enhance CSS with minor improvements
* Update locales for Esperanto, Spanish, French, Portuguese, Galician
and Catalan