Update README.md

Author: xiuliren

README.md

@@ -3,6 +3,8 @@ ZNN v4
 
 [![Build Status](https://travis-ci.org/seung-lab/znn-release.svg?branch=master)](https://github.com/seung-lab/znn-release)
 
+**Documentation**: http://znn-release.readthedocs.org/en/latest/index.html#](http://znn-release.readthedocs.org/en/latest/index.html#)
+
 Required libraries
 ------------------
 Supports Linux and MacOS. When using MKL fftw is not required
@@ -14,7 +16,6 @@ Supports Linux and MacOS. When using MKL fftw is not required
 |[BoostNumpy](http://github.com/ndarray/Boost.NumPy)|NA|
 |[jemalloc](http://www.canonware.com/jemalloc/)|libjemalloc-dev|
 
-
 Compiler flags
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