Feature / Fix: Forward compatibility with future EventLoop v1.0 and v0.5 and cap small timeout values for legacy EventLoop (#26 by @clue)

// now works across all versions
Block\sleep(0.000001, $loop);

Feature / Fix: Throw UnexpectedValueException if Promise gets rejected with non-Exception (#27 by @clue)

// now throws an UnexceptedValueException
Block\await(Promise\reject(false), $loop);

First class support for legacy PHP 5.3 through PHP 7.1 and HHVM (#24 and #25 by @clue)

Improve testsuite by adding PHPUnit to require-dev and Fix HHVM build for now again and ignore future HHVM build errors (#23 and #24 by @clue)