版本：
文件：
- https://cdn.bootcdn.net/ajax/libs/leaflet.toolbar.js/0.3.0/leaflet.toolbar-src.css
- https://cdn.bootcdn.net/ajax/libs/leaflet.toolbar.js/0.3.0/leaflet.toolbar-src.js
- https://cdn.bootcdn.net/ajax/libs/leaflet.toolbar.js/0.3.0/leaflet.toolbar.css
- https://cdn.bootcdn.net/ajax/libs/leaflet.toolbar.js/0.3.0/leaflet.toolbar.js