New: edit readme guide user to implement error process

readme.md

@@ -22,9 +22,10 @@ dependencies {
  		 "clientSecret")
  .subscribeOn(Scedulers.io())
  .observeOn(AndroidScedulers.mainThread())
- .subscribe{
-     it.toString
- }
+ .subscribe({
+    it.toString()
+ },{
+   	it.printStackTrace()})
 ```