Save track files in new Sound model:

* Consolidate migrations
* Add Sound model. Each sound can belong to a track and contains
  informations about one sound file.

app/models/sound.rb

@@ -0,0 +1,18 @@
+require 'fileutils'
+
+class Sound < ActiveRecord::Base
+  belongs_to :track
+
+  validates_presence_of :sha256
+  validates_presence_of :mime_type
+
+  def path
+    "#{Rails.root}/data/sounds/#{sha256}"
+  end
+
+  def file=(file)
+    self.sha256 = Digest::SHA256.file(file.path).hexdigest
+    FileUtils.cp file.path, path
+    self.mime_type = file.content_type
+  end
+end

app/models/track.rb

@@ -1,19 +1,20 @@
 class Track < ActiveRecord::Base
-  validates_presence_of :name
-  validates_presence_of :mime_type
-  validates_presence_of :sha256
+  has_many :sounds
 
-  def filepath
-   "#{Rails.root}/data/tracks/#{sha256}"
+  attr_accessible :name, :file
+
+  validates_presence_of :name
+
+  def file=(file)
+    sounds.build({:file => file})
   end
 
-  def save_with_file(file, mime_type)
-    self.sha256 = Digest::SHA256.file(file.path).hexdigest
-    self.mime_type = mime_type
-    File.open(filepath, 'w') do |f|
-      f.write file.read
-    end
-    save!
+  def sound
+    sounds.first
+  end
+
+  def sound?
+    sounds.any?
   end
 
   def self.latest