* 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.
