Feature spec for creating a new match

id attributes for input fields have to be manually set to make them unique. This helps writing the tests and abides to html rules of not having different elements with the same id.
@bumi agreed
@namxam 
1. "team1[]" becomes team1_ in the id attribute for more than one select tag which is by standard wrong.
2. It's way easier and more readable to write: `fill_in 'set1_team1', with: '6'` instead of something like `fill_in find('#team1_').first, with: '6'`. The latter looks more fragile and can fail for many reasons.