Fix: Explicitly close all STDIO streams when terminating (#45 by @clue)

First class support for legacy PHP 5.3 through PHP 7.1 and HHVM (#47 and #44 by @clue)

Improve testsuite by adding PHPUnit to require-dev and Fix HHVM build for now again and ignore future HHVM build errors (#44 and #46 by @clue)

Improve documentation for mixing asynchronous and synchronous code and fix documentation for $selected argument for radio and checkbox dialogs and restructure examples to ease getting started (#42 and #41 by @bertvandepoel and #48 by @clue)