Make ReverseFileReader autocloseable.

Because why not?

Change-Id: I996ff53c4bb7bd0d237691c260ed7dc55e6499fa
Reviewed-on: http://gerrit.dmdirc.com/4048
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager

src/com/dmdirc/util/io/ReverseFileReader.java

 /**
  * Reads a file in reverse.
  */
-public class ReverseFileReader {
+public class ReverseFileReader implements AutoCloseable {
 
     /** Path to the file we're reading. */
     private final Path file;
         seekLength = newValue;
     }
 
-    /**
-     * Close the file pointer.
-     * This should be called before removing the reference to this object
-     *
-     * @throws IOException If there is an error closing the file, or if it has been closed already.
-     */
+    @Override
     public void close() throws IOException {
-        if (!byteChannel.isOpen()) {
-            throw new IOException("Channel has been closed.");
+        if (byteChannel.isOpen()) {
+            byteChannel.close();
         }
-        byteChannel.close();
     }
 
     /**

test/com/dmdirc/util/io/ReverseFileReaderTest.java

         reader.close();
     }
 
-    @Test(expected=IOException.class)
-    public void testIllegalClose() throws URISyntaxException, IOException {
+    public void testCloseIsIdempotent() throws URISyntaxException, IOException {
         final ReverseFileReader reader = new ReverseFileReader(
                 Paths.get((getClass().getResource("test1.txt").toURI())));
         reader.close();