Integrate third party library like unirest.io/php.html

Unirest could have been bundled as a package too, in which case it would have gone inside application/third_party.

If you write a *library* that wraps an external "package", that would go inside application/libraries.
If you write a *package* that wraps an external "package", that would go inside application/third_party.
These are two different ways of achieving a similar effect.

If the external "package" includes classes, models and views, it would be better as a *package*.
Unirest was simple enough that I kept it as a library.