Refactor readers for better di (#457)

* Refactor readers to get a proper DI

Similar to what was done with writers, readers also needed to be updated to match the new way of doing things.
This commits promotes a better DI (factories, injection through constructors).

* Escapers should not be singletons

Instead, they should be proper object that can be injected where needed.

src/Spout/Common/Creator/HelperFactory.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace Box\Spout\Common\Creator;
+
+use Box\Spout\Common\Helper\EncodingHelper;
+use Box\Spout\Common\Helper\FileSystemHelper;
+use Box\Spout\Common\Helper\GlobalFunctionsHelper;
+
+/**
+ * Class HelperFactory
+ * Factory to create helpers
+ *
+ * @package Box\Spout\Common\Creator
+ */
+class HelperFactory
+{
+    /**
+     * @return GlobalFunctionsHelper
+     */
+    public function createGlobalFunctionsHelper()
+    {
+        return new GlobalFunctionsHelper();
+    }
+
+    /**
+     * @param string $baseFolderPath The path of the base folder where all the I/O can occur
+     * @return FileSystemHelper
+     */
+    public function createFileSystemHelper($baseFolderPath)
+    {
+        return new FileSystemHelper($baseFolderPath);
+    }
+
+    /**
+     * @param GlobalFunctionsHelper $globalFunctionsHelper
+     * @return EncodingHelper
+     */
+    public function createEncodingHelper(GlobalFunctionsHelper $globalFunctionsHelper)
+    {
+        return new EncodingHelper($globalFunctionsHelper);
+    }
+}