Merge pull request #172 from wayslog/master

add multirust into SUMMARY

Author: WaySLOG

SUMMARY.md

@@ -5,6 +5,7 @@
   * [Linux](./02-install/02-01-install_rust_on_linux.md)
   * [Mac](./02-install/02-02-install_rust_on_mac_os.md)
   * [Windows](./02-install/02-03-install_rust_on_windows.md)
+  * [版本管理工具: multirust](./02-install/02-04-multirust.md)
 * [编辑器](./03-editors/03-00-preface.md)
   * [前期准备](./03-editors/03-01-before.md)「wayslog」
   * [vim](./03-editors/03-02-vim.md)「wayslog」