Fix testing(example) folder JS paths

[miqoo1996]

I have cloned this project for understanding how it works.
You have a folder with name example, there are HTML files in the files head section there is an included file "<script src="../pjax.js"></script>" This pjax.js I can't find I think possible that it doesn't exist.

When I'm opening the project/example/index.html file on browser and want to check how it work at that time I'm getting an error, browser says that there isn't pjax.js.
Also I tried to run it by terminal command "npm run example" => http://localhost:3000/example/.

The error need to be Fixed as I think the example folder was created for developers for easly checking and understanding this libary(package).

Thanks, Miqayel.