Docs + Travis CI updates

moved all support files into docs directory, updated and added missing templates (pull request and issue)
updated composer.json
fixed spacing in LICENSE.md
updated .gitattributes and .gitignore
updated Travis CI configuration
- updated legacy dependencies
- removed composer self-update
- removed allow_failures on PHP 7.2
- moved cs-checks and coverage to run on PHP 7.1 with locked dependencies

zendframework / zend-expressive-twigrenderer