Tests: fix coverage generator

version 6.1.0

clean up and minor improvements

fixed backward compatibility and typos

move to Contributte

added GitHub Actions for tests

improvements:

- added config tempDir for mPDF (closes #22) thx @romanmatyus
- typo

Merge pull request #29 from janbarasek/patch-1

PdfResponse: Add strict type support.

Merge pull request #32 from petrparolek/php7.4

Php7.4

Support for nette 3.0 and php 7.3 (#26)

* Updated dependencies, migrated to PSR-4, Updated to PHP 7.1
* Updated pdf test output files