Make the relationship between the Reporter and Closeable interfaces e…

…xplicit. (#1307)

* Resolves #1305 and reimplements #743. Credit to @obfischer for the initial implementation.

* Fix Code Climate check and call out the java.io.Closeable interface in JmxReporter and ScheduledReporter

* Incorporate feedback about explicit implements in order to maintain binary compatibility

metrics-core/src/main/java/com/codahale/metrics/Reporter.java

@@ -1,8 +1,10 @@
 package com.codahale.metrics;
 
+import java.io.Closeable;
+
 /*
  * A tag interface to indicate that a class is a Reporter.
  */
-public interface Reporter {
+public interface Reporter extends Closeable {
 
 }