Use new "strong parameters" from rails4

app/models/playlist.rb

@@ -1,8 +1,6 @@
 class Playlist < ActiveRecord::Base
   belongs_to :user
 
-  attr_accessible :name
-
   validates_presence_of :user
   validates_presence_of :name
 end

app/models/sound.rb

@@ -3,8 +3,6 @@ require 'fileutils'
 class Sound < ActiveRecord::Base
   belongs_to :track
 
-  attr_accessible :file
-
   validates_presence_of :sha256
   validates_presence_of :mime_type
 

app/models/track.rb

@@ -1,8 +1,6 @@
 class Track < ActiveRecord::Base
   has_many :sounds
 
-  attr_accessible :name, :file
-
   validates_presence_of :name
 
   def file=(file)

app/models/user.rb

@@ -4,7 +4,6 @@ class User < ActiveRecord::Base
   include BCrypt
 
   attr_reader :password
-  attr_accessible :email, :password, :password_confirmation
 
   has_many :playlists