Create version 0.4.3

[simonschoelly]

In response to #121 we should have a new version that adds the latest changes. Therefore this PR does:

• Bump version to 0.4.3
• Add Julia 1.5 to testing pipeline
• Set min Julia version to 1.3 - with 1.0 there where some problems running tests with Cairo

[codecov]

Codecov Report

Merging #122 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #122   +/-   ##
=======================================
  Coverage   33.20%   33.20%           
=======================================
  Files           9        9           
  Lines         524      524           
=======================================
  Hits          174      174           
  Misses        350      350           

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