should add a run param to limit directory access

[Bryant-Yang]

Snakeviz is helpful for my web apis profile, I run snakeviz as a web server so that developers can check their Flask api profile remotely. But by now there is no way to deny directory access. I can even explore '/' by navigator in web page or by url path.

There should be some params to limit the access permission, such as 'snakeviz -s --access-path '.
It should only show the profile files which user want to expose.