Don't show emails or real-names in speaker-select-input

- Fixes #1884
- Decided to remove real names as well, because the profile page
  calls out the username field as "how others users see you"

app/helpers/application_helper.rb

@@ -127,9 +127,13 @@ module ApplicationHelper
   end
 
   def speaker_selector_input(form)
-    users = User.active.pluck(:id, :name, :username, :email).map { |user| [user[0], user[1].blank? ? user[2] : user[1], user[2], user[3]] }.sort_by { |user| user[1].downcase }
+    users = User.active.pluck(:id, :username).map { |user| 
+      [user[0], user[1]] 
+    }.sort_by { |user| 
+      user[1].downcase 
+    }
     form.input :speakers, as: :select,
-                          collection: options_for_select(users.map {|user| ["#{user[1]} (#{user[2]}) #{user[3]}", user[0]]}, @event.speakers.map(&:id)),
+                          collection: options_for_select(users.map {|user| [user[1], user[0]]}, @event.speakers.map(&:id)),
                           include_blank: false, label: 'Speakers', input_html: { class: 'select-help-toggle', multiple: 'true' }
   end