Update specs to new rspec syntax

spec/views/playlists/edit.html.haml_spec.rb

@@ -11,16 +11,16 @@ describe 'playlists/edit' do
 
   it 'renders a form to edit a playlist' do
     render
-    rendered.should have_selector("form[method=post][action='#{playlists_path}']")
-    rendered.should have_selector('input[type=submit]')
+    expect(rendered).to have_selector("form[method=post][action='#{playlists_path}']")
+    expect(rendered).to have_selector('input[type=submit]')
   end
 
   it 'renders a text field with a label for the playlists name' do
-    playlist.stub(name: 'Electro')
+    allow(playlist).to receive(:name) { 'Electro' }
     render
-    rendered.should have_selector(
-      "input[type=text][name='playlist[name]'][value=Electro]"
-    )
-    rendered.should have_selector("label[for=playlist_name]", text: 'Name')
+    expect(rendered)
+      .to have_selector "input[type=text][name='playlist[name]'][value=Electro]"
+    expect(rendered)
+      .to have_selector 'label[for=playlist_name]', text: 'Name'
   end
 end