Hexadecimal color changed to capital letters

The default colors in event_types and difficulty levels are in capital letters and the ones that comes from the color picker were not. Now colors are capitalized before saving the track, level or type. A rake task has also been created to capitalize color from old tracks, levels or types.

spec/views/admin/difficulty_levels/index.html.haml_spec.rb

@@ -9,6 +9,6 @@ describe 'admin/difficulty_levels/index' do
     render
     expect(rendered).to include('Example Difficulty Level')
     expect(rendered).to include('Lorem Ipsum dolsum')
-    expect(rendered).to include('#ffffff')
+    expect(rendered).to include('#FFFFFF')
   end
 end