FormBuilderTest: testSelect: added test for '0'-key option
FormBuilderTest: testSelect: added test for '0'-key option

Added assertion for the case, that the options for the select field contain a zero key, eg `['0' => 'All Sizes', 'L' => 'Large']`

See also commit: https://github.com/LaravelCollective/html/pull/127/commits
laravie/html,djh101/html,sebdesign/html,LaravelCollective/html