Fixes arr.contains typo
Fixes arr.contains typo

See https://github.com/emberjs/website/pull/2600#discussion_r71019852
bmac/website,josemarluedke/ember-website,josemarluedke/ember-website,bmac/website,SaladFork/emberjs-website,bmac/website,SaladFork/emberjs-website,kpfefferle/website,AaronSikes/website,bmac/website,SaladFork/emberjs-website,kpfefferle/website,SaladFork/emberjs-website,josemarluedke/ember-website,josemarluedke/ember-website,AaronSikes/website,kpfefferle/website,AaronSikes/website