Migrate to illuminate/collections

[hackel]

Your README states that you depend on Tightenco\Collect, but that package has been deprecated in favour of the official upstream illuminate/collections package (which is also provided by laravel/framework). Curiously, you don't even seem to use that package in favour of your own pragmarx/ia-collection, which could also be deprecated as far as I can tell.

This would be nice to reduce the amount of duplicate code I'm pulling in a Laravel project, and certainly be easier for you to maintain without having to check for and pull in any upstream changes all the time. Mostly though it's just a pet-peeve that I've always got to search for the correct Collection/Arr/Str classes to use when I just want the official ones.