fix default/httpd.mime Z file extension to lower case

+ test case

defaults/httpd.mime

@@ -136,6 +136,6 @@ xltx    = application/vnd.openxmlformats-officedocument.spreadsheetml.template
 xpi     = application/x-xpinstall
 xsl     = text/xml
 xml     = text/xml
-Z       = application/x-compress
+z       = application/x-compress
 zip     = application/zip
 default = application/octet-stream

test/java/net/yacy/cora/document/analysis/ClassificationTest.java

@@ -0,0 +1,50 @@
+/**
+ *  ClassificationTest
+ *  part of YaCy
+ *  Copyright 2017 by reger24; https://github.com/reger24
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Lesser General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2.1 of the License, or (at your option) any later version.
+ *
+ *  This library is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public License
+ *  along with this program in the file lgpl21.txt
+ *  If not, see <http://www.gnu.org/licenses/>.
+ */
+package net.yacy.cora.document.analysis;
+
+import java.io.File;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+/**
+ * Unit tests for Classification class.
+ */
+public class ClassificationTest {
+
+    /**
+     * Initialize with default file ext to mime file
+     */
+    @BeforeClass
+    public static void setUpClass() {
+        Classification.init(new File("defaults/httpd.mime"));
+    }
+
+    /**
+     * Test of ext2mime method, of class Classification.
+     */
+    @Test
+    public void testExt2mime_String() {
+        String mime;
+        mime = Classification.ext2mime("Z");
+        assertEquals("application/x-compress", mime);
+    }
+
+}