v2.0.0

• Support for Django 3.1
• Tests with django-tables2 v2.3
• Add support for Bootstrap5 - issue #19
• Add special classes ColumnShiftTableBootstrap3,
  ColumnShiftTableBootstrap4 and ColumnShiftTableBootstrap5
• Change default inherit for django_tables2_column_shifter/templtes/table.html
  from django_tables2_column_shifter/bootstrap.html to django_tables2_column_shifter/bootstrap4.html
  so class ColumnShiftTable by default call bootstrap4 template from django-tables2 - refere to issue #18

If you use different bootstrap version then 4 please use one of class: ColumnShiftTableBootstrap2/3/4/5