Adds Larastan

[nunomaduro]

This Pull Request adds nunomaduro/larastan as require-dev dependency. Larastan is a wrapper of PHPStan, and is a static analysis tool for PHP.

About Phpstan: "PHPStan is a static analysis tool for PHP code. It parses your code and tries to find flaws in the program logic (like a variable being used before being declared, or a function being called that does not exist...). It is not the ultimate tool for catching bugs but it has one huge advantage: it does not need a lot work to set up! No need to write unit tests, simply run the tool and it will output a list of potential errors!".

You can read more in this article: medium.com/@ondrejmirtes/phpstan-2939cd0ad0e3

This Pull Request also fixes the errors detected until level 5.

Usage:

./vendor/bin/phpstan analyse

Notes:

• You can choose from currently 8 levels: (0 is the loosest and 7 is the strictest) by passing --level option: ./vendor/bin/phpstan analyse --level=5.
• Larastan is not stable yet. But I am using it in all my projects and packages.
• The line ./vendor/bin/phpstan analyse was added to .travis file.

[nunomaduro]

Any plans of merging this? I am cleaning up my opens PRs.

[mpociot]

Thanks for this @nunomaduro , I'll add Larastan myself in order to avoid having to resolve the conflicts of a rather old codebase.