Implement track/stream

* Add Streamer class
* Use FactoryGirl for factories
* Add sha256 field to tracks
* Add mime_type field to tracks

db/migrate/20110725110405_add_mime_type_field_to_tracks.rb

@@ -0,0 +1,9 @@
+class AddMimeTypeFieldToTracks < ActiveRecord::Migration
+  def self.up
+    add_column :tracks, :mime_type, :string
+  end
+
+  def self.down
+    remove_column :tracks, :mime_type
+  end
+end

db/migrate/20110726101228_add_sha256_field_to_tracks.rb

@@ -0,0 +1,9 @@
+class AddSha256FieldToTracks < ActiveRecord::Migration
+  def self.up
+    add_column :tracks, :sha256, :string
+  end
+
+  def self.down
+    remove_column :tracks, :sha256
+  end
+end