README with SerialInputOutputManager for read() and port for write()

test the usually not used read/write variants

usbSerialForAndroid/src/main/java/com/hoho/android/usbserial/util/SerialInputOutputManager.java

@@ -50,7 +50,7 @@ public class SerialInputOutputManager implements Runnable {
     // Synchronized by 'mWriteBuffer'
     private final ByteBuffer mWriteBuffer = ByteBuffer.allocate(BUFSIZ);
 
-    private enum State {
+    public enum State {
         STOPPED,
         RUNNING,
         STOPPING
@@ -111,7 +111,7 @@ public class SerialInputOutputManager implements Runnable {
         }
     }
 
-    private synchronized State getState() {
+    public synchronized State getState() {
         return mState;
     }