Updated code sniffer dependency.

Fixed spacing in README.

Resolves #2.

Travis builds for PHP 8.0.

Removed support for PHP 7.2

Running tests in PHP 7.2 -> 7.4

Merge branch 'master' of github.com:guillermoandrae/php-collection

Merge pull request #1 from guillermoandrae/0.2.x

0.2.0

Got rid of the JsonableTrait--bad design.