*Drop Python2 support, change configuration filename and some minor improvements*
* **[Backward incompatible]** Drop Python2 support (remove six, unicode litteral,
update package configuration, etc..);
* **[Backward incompatible]** Changed default configuration filename from
``settings`` to ``boussole``. This was required to avoid clash with some other
projects since "settings" is a too common word;
* Drop ``pathtools`` package dependency since it is an abandoned project;
* Update doc config, use livereload and with new RTD config file;
* Drop support for libsass-python ``<0.19.4``.
* Rename ``requirements_freeze.txt`` to ``frozen.txt``;
* Add a new script for development which help to automatically update the
``frozen.txt`` file;
For new configuration filename change you have two way to resolve it:
* Just change your configuration filename to the new one, like if you were
using ``settings.json``, you will rename it to ``boussole.json``;
* Use option ``--config`` to explicitely use your own configuration filename;