Upgrade dotenv to v3

[fitztrev]

There's an incompatibility with Laravel 5.8 and this because of vlucas/phpdotenv between each's composer.json.

Project	Dependency	Version
laravel/framework	vlucas/phpdotenv	^3.3
beyondcode/laravel-self-diagnosis	vlucas/phpdotenv	~2.5

I know this PR's current state is not the best way to fix it (unless you want to release a new major version), as it will break backwards compatibility, but here's a first attempt to hopefully help at least get it started. This fixes it for 5.8.

[tvbeek]

I think this should result in a version 2.0 because of the backwards compatibility break. And also #72 need to be merged to make it Laravel 5.8 compatible. See: https://laravel.com/docs/5.8/upgrade#string-and-array-helpers

[crynobone]

Why not support both version?

If ^3.3 is installed, you can check against existent of Dotenv\Environment\FactoryInterface (which is not available in 2.3+). This allows you to actually tests against multiple version of Laravel.

It's very sketchy that you claim to support "illuminate/support": "5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*" but only test against "orchestra/testbench": "^3.8" which would only resolved to Laravel 5.8.

[fitztrev]

Updated with backward compatibility. CI is now passing against Laravel 5.6 and 5.8.

It could probably be a minor release now.

[tvbeek]

It's very sketchy that you claim to support "illuminate/support": "5.2.*|5.3.*|5.4.*|5.5.*|5.6.*|5.7.*|5.8.*" but only test against "orchestra/testbench": "^3.8" which would only resolved to Laravel 5.8.

Maybe it is a good idea to create a PR to test for the different versions, but because #60 doesn't get any reaction I'm not sure that @mpociot will place some focus on testing as long as it works.

@fitztrev good update.

[mpociot]

Thank you very much for the work on this! :)