Enable custom classes to override the default threading behavior.

Author: Oriental Sensation

library/src/main/java/com/loopj/android/http/AsyncHttpClient.java

@@ -217,7 +217,7 @@ public AsyncHttpClient(SchemeRegistry schemeRegistry) {
 
         ThreadSafeClientConnManager cm = new ThreadSafeClientConnManager(httpParams, schemeRegistry);
 
-        threadPool = Executors.newCachedThreadPool();
+        threadPool = getDefaultThreadPool();
         requestMap = new WeakHashMap();
         clientHeaderMap = new HashMap();
 
@@ -348,6 +348,15 @@ public ExecutorService getThreadPool() {
         return threadPool;
     }
 
+    /**
+     * Get the default threading pool to be used for this HTTP client.
+     *
+     * @return The default threading pool to be used
+     */
+    protected ExecutorService getDefaultThreadPool()  {
+        return Executors.newCachedThreadPool();
+    }
+
     /**
      * Simple interface method, to enable or disable redirects. If you set manually RedirectHandler
      * on underlying HttpClient, effects of this method will be canceled.