Bumped version to 1.3.0

[FinalAngel]

• Added support for Django 2.2 and django CMS 3.7
• Removed support for Django 2.0
• Extended test matrix
• Exclude tests folder from release build
• Added installation instructions for django-filer

[codecov-io]

Codecov Report

Merging #87 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #87   +/-   ##
=======================================
  Coverage   72.56%   72.56%           
=======================================
  Files          11       11           
  Lines         226      226           
  Branches       21       21           
=======================================
  Hits          164      164           
  Misses         61       61           
  Partials        1        1

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