Radio button checked by default when using ng-repeat

http://stackoverflow.com/questions/29539549/radio-button-checked-by-default-when-using-ng-repeat
http://stackoverflow.com/questions/25443018/angularjs-is-it-possible-to-deselect-html-radio-input-by-click
http://stackoverflow.com/questions/22498198/each-alternative-in-angular-js