Use ruby 2.x hash syntax

app/controllers/api/application_controller.rb

@@ -1,6 +1,6 @@
 class API::ApplicationController < ApplicationController
   skip_before_filter :verify_authenticity_token
-  skip_before_filter :authenticate!, :only => [:cor_preflight]
+  skip_before_filter :authenticate!, only: [:cor_preflight]
 
   before_filter :cor_filter
 

app/controllers/api/sessions_controller.rb

@@ -1,11 +1,11 @@
 class API::SessionsController < API::ApplicationController
-  skip_before_filter :authenticate!, :only => [:create]
+  skip_before_filter :authenticate!, only: [:create]
 
   def create
     user = User.find_by_email(params[:session][:email])
 
     if ! user.try(:authenticate?, params[:session][:password])
-      return render :json => '', :status => :not_found
+      return render json: '', status: :not_found
     end
 
     @user = user

app/controllers/api/sounds_controller.rb

@@ -2,6 +2,6 @@ class API::SoundsController < API::ApplicationController
   # FIXME: add some tests!
   def show
     sound = Sound.find params[:id]
-    send_file sound.path, :type => sound.mime_type
+    send_file sound.path, type: sound.mime_type
   end
 end