📚 Add description and links to knitpy and stittch

Author: kozo2

README.md

@@ -3,8 +3,17 @@
 [![CircleCI](https://circleci.com/gh/sciruby-jp/rubydown/tree/master.svg?style=svg)](https://circleci.com/gh/sciruby-jp/rubydown/tree/master)
 [![Build status](https://ci.appveyor.com/api/projects/status/rroa24x9jgdwuka5?svg=true)](https://ci.appveyor.com/project/kozo2/rubydown)
 
-
 *rubydown* is pure-Ruby [R Markdown](https://rmarkdown.rstudio.com/) clone.
+It takes a markdown source file, executes the code chunks, captures the output, and stitches the output into the destination file.
+
+Python also has R Markdown like packages.
+If you have interest about making reproducible reports, please also refer to the following projects.
+
+https://github.com/jankatins/knitpy
+
+https://github.com/pystitch/stitch
+
+
 
 ## Quick Start