Implemented the ability to override the instance of ZipContainer.

ZipContainer will be cloned before writing the zip file.
Tested custom ZipWriter, ZipReader, ZipContainer and ZipFile.

tests/Internal/Epub/EpubZipContainer.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace PhpZip\Tests\Internal\Epub;
+
+use PhpZip\Exception\ZipEntryNotFoundException;
+use PhpZip\Model\ZipContainer;
+
+/**
+ * Class EpubZipContainer.
+ */
+class EpubZipContainer extends ZipContainer
+{
+    /**
+     * @throws ZipEntryNotFoundException
+     *
+     * @return string
+     */
+    public function getMimeType()
+    {
+        return $this->getEntry('mimetype')->getData()->getDataAsString();
+    }
+}