fix the potential threat when use "uri = uri + '/' " to bypassed shiro protect

hi, the potential threat found when use shiro filter.
in spring web, the requestURI : /resource/menus and resource/menus/ both can access the resource,
but the pathPattern match /resource/menus can not match resource/menus/
user can use requestURI + "/" to simply bypassed chain filter, to bypassed shiro protect

[PR #127|https://github.com/apache/shiro/pull/127]