Replace deprecated ugettext_lazy with gettext_lazy

Fix package description

Add black code linter

Pin python measurement dependency to < 4.0

Replaced django 2.0 from the CI to latest LTS & include Python 3.7 + 3.8

Replace deprecated logger.warn with logger.warning

Fix #11 -- Add custom measurement class support (#76)

Add Django 2.0 support

* Drop support for Python 2
* Drop support for Django 1.8
* Drop support for Django 1.10
* Add pbr to simplify releases
* Add travis based deploys
* Add CodeCov
* Update readme

Added bidimensional_separator setting/kwarg (#29)

unit_choices via .get_units(); unicode labels