Clean up dead links about mapstruct.org

[mviku]

There are 3 places that still needs to be update:

1. The CI build link in Contributing -> Could be updated to the travis link
2. The API docs references in Technical documentation -> The links could be updated to the stable static documentation in http://mapstruct.org/documentation/stable/api/
3. The CI server reference in an old [news feed])(http://mapstruct.org/news/2015-03-05-arrays-configuration-inheritance-mapstruct-1_0_0_Beta4/) -> This probably could be updated to the latest released version in https://dl.bintray.com/mapstruct/mapstruct-eclipse-site/

[gunnarmorling]

@filiphr, just came here to report the CI link, but saw it's know for two years ;) Where's CI running these days? I can update the page.

[filiphr]

@gunnarmorling we are now using GitHub Actions this is the link we use in our Readme page.

[gunnarmorling]

Ha, ok :) Updated it. Thx!

[filiphr]

Awesome, thanks :)