Provide PHP 7.2 support

[weierophinney]

• Results of running zf-maintainer rebase-doc-templates

• Updates dependencies

  • zend-mvc to 2.7.15
  • phpunit to 5.7, 6.5, or 7.1
  • swap in zend-coding-standard for vanilla phpcs

  Code/test changes are the result of running phpcbf, and updating tests to work with new PHPUnit APIs.

• Updates Travis configuration

  • Remove HHVM jobs
  • Add jobs for PHP 7.1 and 7.2
  • Use modern install script
  • Update scripts to match other repos

Fixes #16