update readme, add product wiki link

@@ -68,6 +68,7 @@ cd simple-rtmp-server/trunk
 [Usage: How to deploy srs on ARM?](https://github.com/winlinvip/simple-rtmp-server/wiki/SampleARM)<br/>
 [Usage: How to show the demo of SRS?](https://github.com/winlinvip/simple-rtmp-server/wiki/SampleDemo)<br/>
 [Usage: Solution using SRS?](https://github.com/winlinvip/simple-rtmp-server/wiki/Sample)<br/>
+[Usage: Why SRS?](https://github.com/winlinvip/simple-rtmp-server/wiki/Product)<br/>
 
 ### System Requirements
 Supported operating systems and hardware:

@@ -255,7 +255,7 @@ private:
 /**
 * delivery RTMP stream to HLS(m3u8 and ts),
 * SrsHls provides interface with SrsSource.
-*
+* TODO: FIXME: add utest for hls.
 */
 class SrsHls
 {