Multiple fixes

* Implemented ScriptRunner with environment expansion and cleaner
  code.
* Added ApiClient plugin (com.noccy.apiclient)
* Renamed CHANGELOG.md to VERSIONS.md
* Shuffled buildtools
* Added first unittests

tests/Environment/ScriptRunnerTest.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace Spark\Environment;
+
+
+
+class ScriptRunnerTest extends \PhpUnit\Framework\TestCase
+{
+    /**
+     * @dataProvider stringExpansionData
+     * @covers ScriptRunner::expandString
+     */
+    public function testStringExpansion($source, $expect)
+    {
+        $runner = new ScriptRunner();
+        $expanded = $runner->expandString($source);
+        return $this->assertEquals($expect, $expanded);
+    }
+
+    public function stringExpansionData()
+    {
+        return [
+            [ 'Hello World!', 'Hello World!' ],
+            [ '${testenv}', '' ],
+            [ '${PATH}', getenv("PATH") ],
+            [ 'Greetings ${USER}', 'Greetings '.getenv("USER") ],
+        ];
+    }
+
+}