* Add regex for title text version of links
Original parser matched:
[name](http:://link)
Add match for:
[name](http:://link "title text")
* Add tests and improve regex's
* Several new tests in test_maddy_linkparser.cpp (Some with paths for future improvement, and one to ensure an overzealous future update doesn't disallow actually-used special characters like o-umlaut).
* URLs now ignore leading/trailing spaces.
* URLs now don't match on internal spaces or quotes.
* Small grammar fix in CONTRIBUTING.md
* Updated changelog.
cmake configuration for running tests is now in the
tests folder.
Add option in main cmake file that has to be set to
ON and only build the tests in that case.
Update appveyor and travis ci configurations accordingly.
cmake minimum required version is now 3.25.
Instead of loading gtest via git submodule, it is now loaded
in the cmake files.
gtest version upped to v1.13.0.
