Allow symfony/finder ^5.0

Merge pull request kss-php#3 from vnq/symfony4Support

Allows for symfony/finder v4 and up

Adds Symfony 3 support

Removes Scan namespace

Adss parameter block support, fixes compatibility block to match spec…

…, adds support for stylus

Makes Section Match Methods case insensitive.

Treat "No styleguide reference" as a valid KSS Block. Adds hasReferen…

…ce to Section.

Fix for the word "styleguide" being matched in other sections of a KS…

…S Block.

Adds support for non-numeric styleguide references.

Adds compatibility comments and changes to psr-4.