update readme.md for python3
diff --git a/doc/readme.md b/doc/readme.md
index 9b1349d..75a9891 100644
--- a/doc/readme.md
+++ b/doc/readme.md
@@ -44,9 +44,13 @@
### Viewing
```
-pushd build/html && python -m SimpleHTTPServer 3000
+# python 2
+pushd build/html && python -m SimpleHTTPServer 3000
+
+# python 3
+pushd build/html && python -m http.server 3000
```
### Screenshot
-<img src="https://user-images.githubusercontent.com/1182522/48395569-04995d00-e75b-11e8-87b8-2f28662ef3ca.png">
\ No newline at end of file
+<img src="https://user-images.githubusercontent.com/1182522/48395569-04995d00-e75b-11e8-87b8-2f28662ef3ca.png">