minor, update 1.6 doc links in README.md

Author: lidongsjtu

README.md

@@ -12,7 +12,7 @@ For more details, see the website [http://kylin.apache.org](http://kylin.apache.
 
 Documentation
 =============
-Please refer to [http://kylin.apache.org/docs15/](http://kylin.apache.org/docs15/).
+Please refer to [http://kylin.apache.org/docs16/](http://kylin.apache.org/docs16/).
 
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 ============