Update org.tukaani:xz to 1.8

Closes #85

Author: plamentotev

pom.xml

@@ -89,7 +89,7 @@
     <dependency>
       <groupId>org.tukaani</groupId>
       <artifactId>xz</artifactId>
-      <version>1.6</version>
+      <version>1.8</version>
       <scope>runtime</scope>
     </dependency>
   </dependencies>