Fix for issue #414 (#415)

* update doc for "write trial"

* fix link

* issue 414

docs/howto_1_WriteTrial.md

@@ -113,7 +113,7 @@ with tf.Session() as sess:
 >>
 >>`@nni.report_intermediate_result`/`@nni.report_final_result` will send the data to assessor/tuner at that line. 
 >>
->>Please refer to [Annotation README](../tools/annotation/README.md) for more information about annotation syntax and its usage. 
+>>Please refer to [Annotation README](../tools/nni_annotation/README.md) for more information about annotation syntax and its usage. 
 
 
 >Step 2 - Enable NNI Annotation

tools/nni_annotation/README.md

-# Introduction 
+# NNI Annotation Introduction 
 
 For good user experience and reduce user effort, we need to design a good annotation grammar.