Rails4でエラー：You should not use the `match` method in your router without specifying an HTTP method. (RuntimeError)

rails s

を実行時に，「You should not use the `match` method in your router without specifying an HTTP method. (RuntimeError)」とエラーが出た際には，routes.rbに「match」メソッドが含まれていることが原因．

例えば，

 root :to => 'thread#index'
 match '/' => 'thread#index'
 match '/about' => 'thread#about'

を

 root :to => 'thread#index'
 get '/' => 'thread#index'
 get '/about' => 'thread#about'

のように変えればOK．