[5.6] Form method of hidden input '_method' is preserved on next requ…
…est (#486)
* Form method of hidden input '_method' is preserved on next request
E.G. When you submitted data across a form with a 'PATCH' method and then in a second submit you use a form with a 'DELETE' method, the FormBuilder::getValueAttribute() method use the previous value of the hidden input '_method'.
So the value is replaced by 'PATCH' instead of the 'DELETE' value.
* Drop PHP 7.1 and add PHP 7.2 in Travis CI config
Because Laravel 5.6 require at least PHP 7.1.3
* Fix PHP 7.2 Warning with count()
Otherwise a PHP Warning is thrown:
count(): Parameter must be an array or an object that implements Countable
See http://php.net/manual/en/migration72.incompatible.php#migration72.incompatible.warn-on-non-countable-types
* Bump Mockery version to support PHP 7.2
