Fix file descriptor leak

`JarArchiver` and `PlexusIoZipFileResourceCollection`
use `Closeable` classes but does not close them.
That leads to file descriptor leaks as
the opened files are not closed.

Fixes #79

Author: plamentotev

src/main/java/org/codehaus/plexus/archiver/jar/JarArchiver.java

@@ -484,7 +484,10 @@ protected void zipFile( InputStreamSupplier is, ConcurrentJarCreator zOut, Strin
         {
             if ( !doubleFilePass || skipWriting )
             {
-                filesetManifest( fromArchive, is.get() );
+                try ( InputStream manifestInputStream = is.get() )
+                {
+                    filesetManifest( fromArchive, manifestInputStream );
+                }
             }
         }
         else if ( INDEX_NAME.equalsIgnoreCase( vPath ) && index )

src/main/java/org/codehaus/plexus/archiver/zip/PlexusIoZipFileResourceCollection.java

@@ -196,7 +196,14 @@ public void remove()
         public void close()
             throws IOException
         {
-            zipFile.close();
+            try
+            {
+                urlClassLoader.close();
+            }
+            finally
+            {
+                zipFile.close();
+            }
         }
 
     }