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/Node/Expr/ShellExec.php

@@ -0,0 +1,30 @@
+<?php declare(strict_types=1);
+
+namespace PhpParser\Node\Expr;
+
+use PhpParser\Node\Expr;
+
+class ShellExec extends Expr
+{
+    /** @var array Encapsed string array */
+    public $parts;
+
+    /**
+     * Constructs a shell exec (backtick) node.
+     *
+     * @param array $parts      Encapsed string array
+     * @param array $attributes Additional attributes
+     */
+    public function __construct(array $parts, array $attributes = []) {
+        $this->attributes = $attributes;
+        $this->parts = $parts;
+    }
+
+    public function getSubNodeNames() : array {
+        return ['parts'];
+    }
+    
+    public function getType() : string {
+        return 'Expr_ShellExec';
+    }
+}