Updates array syntax and removes YU

[ivanciric]

Changes the syntax from array() to [], available since PHP 5.4. Removes Yugoslavia (YU) from list as it doesn't exist anymore since 1991.

[ivanciric]

Hi @Stroemgren , I was searching for an easy to use country list to add to a Laravel seeder and came across this little gem of yours :) Since it helped a lot and saved a bunch of time, I decided to humbly contribute a tiny bit. Thank you!