Refactorings

- important curl and wget improvements
- initial test coverage
- setters and getters in Request classes
- namespace fixes
- some additions in README
- docblocks and code-style

src/Converters/ConverterContract.php

@@ -0,0 +1,11 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PmConverter\Converters;
+
+interface ConverterContract
+{
+    public function convert(object $collection, string $outputPath): void;
+    public function getOutputPath(): string;
+}