Add a possibility to wire a health check executor

pom.xml

@@ -3,7 +3,7 @@
 	<modelVersion>4.0.0</modelVersion>
 	<groupId>com.ryantenney.metrics</groupId>
 	<artifactId>metrics-spring</artifactId>
-	<version>3.0.3</version>
+	<version>3.0.4</version>
 	<packaging>bundle</packaging>
 	<name>Metrics Spring Integration</name>
 	<description>Spring integration for Coda Hale's Metrics Library</description>

src/main/java/com/ryantenney/metrics/spring/servlets/MetricsServletsContextListener.java

@@ -15,6 +15,7 @@
  */
 package com.ryantenney.metrics.spring.servlets;
 
+import java.util.concurrent.ExecutorService;
 import javax.servlet.ServletContextEvent;
 import javax.servlet.ServletContextListener;
 
@@ -34,6 +35,9 @@ public class MetricsServletsContextListener implements ServletContextListener {
 	@Autowired
 	private HealthCheckRegistry healthCheckRegistry;
 
+    @Autowired(required = false)
+    private ExecutorService healthChecksExecutorService;
+
 	private final MetricsServletContextListener metricsServletContextListener = new MetricsServletContextListener();
 	private final HealthCheckServletContextListener healthCheckServletContextListener = new HealthCheckServletContextListener();
 
@@ -64,6 +68,14 @@ protected HealthCheckRegistry getHealthCheckRegistry() {
 			return healthCheckRegistry;
 		}
 
-	}
+        @Override
+        protected ExecutorService getExecutorService() {
+            if (healthChecksExecutorService != null) {
+                return healthChecksExecutorService;
+            } else {
+                return super.getExecutorService();
+            }
+        }
+    }
 
 }