[Feat] Added support for Laravel attribute setters in Laravel preset

[olivernybroe]

Q	A
Bug fix?	yes
New feature?	yes
Fixed tickets	#135

This PR adds support for the Laravel set attribute syntax without showing it as an error.

This has been implemented by creating a custom Sniff for setters which replaces the one we used from a package. This new sniff has support for filtering methods based on a regex.

In the Laravel Preset the regex for Laravel attribute setters has been added in as methods which to ignore.

resolves: #135

[olivernybroe]

@nunomaduro This PR also adds an example for testing that the Laravel Preset actually ignores attribute setters. It is not a bullet proof way, as it just checks if any errors are present in the Classes metric.

[nunomaduro]

Sounds awesome, going to check this tonight.

[nunomaduro]

@olivernybroe Thanks for this pull request. Actually I think we can do better on this: A generic feature where on the configuration you can ignore errors globally or on specific classes. What do you think?

[olivernybroe]

@nunomaduro I like the idea of adding that in to ignore errors in a more broad way. However for it to work good enough to replace this sniff, it has to be specific enough to I can ignore an error based on the naming of a method with a regex.

This PR still disallows setters in models, but just ignores them if they are laravel setters. The Sniff itself just has support for ignoring methods based on a regex.

My opinion would be to first merge this in, as we are going to need custom sniff in some cases and fixing an issue like this is pretty important as a lot of users are using laravel mutators.
Then we can work on setting up a generic way to ignore classes.

[nunomaduro]

@olivernybroe Alright! Can you just check why tests are not passing?

[nunomaduro]

Very good job! Thanks for this @olivernybroe. Fell free to perform the next release: https://github.com/nunomaduro/phpinsights/blob/master/RELEASE.md. Please ask me if you have any questions.