Update CONTRIBUTING

Signed-off-by: Jianhui Zhao <jianhuizhao329@gmail.com>

CONTRIBUTING.md

@@ -25,7 +25,7 @@ If you want to contribute to [libuhttpd](https://github.com/zhaojh329/libuhttpd)
 5. Commit and push your changes, then make a pull request from Github.
 
     git commit --signoff
-    git push
+    git push origin libuhttpd-1-fix
  
 6. Awaiting review, if accepted, merged!
 

CONTRIBUTING_ZH.md

@@ -25,7 +25,7 @@
 5. 提交代码并推送到服务器，然后从Github提交pull request。
 
     git commit --signoff
-    git push
+    git push origin libuhttpd-1-fix
 
 6. 等待审查，如果被接受，你的修改将会被合并到主分支。