Class rename, composer add, phpUnit tests add

Rename the class from ReadEnvFile to DotEnv.
Add everything to a composer json file so it can be published to
composer repository.
Add phpUnit tests for system

vendor/nikic/php-parser/lib/PhpParser/ConstExprEvaluationException.php

@@ -0,0 +1,6 @@
+<?php
+
+namespace PhpParser;
+
+class ConstExprEvaluationException extends \Exception
+{}