Add a very basic custom_css property to a conference.

It is loaded on all pages for that conference.

app/views/admin/conferences/edit.html.haml

@@ -17,6 +17,11 @@
         = image_tag @conference.picture.thumb.url
       = f.input :picture, label: false, hint: 'This will be displayed on the front page.'
       = f.hidden_field :picture_cache
+
+      = f.input :custom_css,
+        hint: "Add Custon CSS to the main page. You might find the class '.conference-#{@conference.short_title}' useful.",
+        input_html: { rows: 5 }
+
       = f.input :ticket_layout, as: :select, collection: Conference.ticket_layouts.keys, hint: "Layout type for tickets of the conference."
       = f.inputs name: 'Scheduling' do
         = f.input :timezone, as: :time_zone, hint: 'The conference time zone'

app/views/layouts/application.html.haml

@@ -21,6 +21,10 @@
       = javascript_include_tag "//cdn.transifex.com/live.js"
 
     = yield(:head)
+    - if @conference && @conference.custom_css?
+      %style{type: 'text/css'}
+        = @conference.custom_css
+
   %body{ class: ("conference-#{@conference.short_title}" if @conference) }
     = render 'layouts/navigation', conference: @conference
     -# Admin area