Add app category output, embed apps.json in package, slight restructure

Chief changes:

* Add apps.json as a local package resource to avoid downloading on package instantiation or manual management by package users. Had some problems with backtracking in regexes from Wappalyzer main repo, so this will let us pick a stable apps.json version to include in the package
* Allow passing in apps.json from local path.
* Restructure package slightly.
* Add analyze_with_categories() function, which returns category names in addition to apps found.

Sounds very reasonable - a good compromise for all use cases. I'll make the adjustments and submit a new PR.