Docs fix for usage as lib example

[leschekfm]

I tried to integrate the module into my own project as lib and found some issues regarding outdated paths and function names in the example code.

Also the example code wasn't working using the promises approach therefore I upgraded the example to async/await (not sure if that's wanted)

[kriskbx]

Thanks for your pull request! I really appreciate it. You're right: there are errors in the docs.

To be honest: I never used async/await before. I just learned about Promises when I ported gtt from PHP to nodejs. (I'm actually a PHP dev) I think I understood the concept behind it, but I definetely lack some experience working with it. I will look into it within the next week and maybe even refactor the core code to async/await as it looks way cleaner then the Promise-chaining I did before.