Was getting these failures after switching the controller over to use a
decorated `@time_table`:

    Failures:

      1) /time_tables/show should render h2 with the time_table comment
         Failure/Error: - @time_table.action_links.each do |link|

         ActionView::Template::Error:
           undefined method `action_links' for #<Chouette::TimeTable:0x007fc8cefb8260>
         # ./app/views/time_tables/show.html.slim:13:in `block in _app_views_time_tables_show_html_slim__2702796193816469913_70250218141540'
         # ./app/helpers/newapplication_helper.rb:246:in `block (2 levels) in pageheader'
         # ./app/helpers/newapplication_helper.rb:244:in `block in pageheader'
         # ./app/helpers/newapplication_helper.rb:243:in `pageheader'
         # ./app/views/time_tables/show.html.slim:4:in `_app_views_time_tables_show_html_slim__2702796193816469913_70250218141540'
         # ./spec/views/time_tables/show.html.erb_spec.rb:15:in `block (2 levels) in <top (required)>'
         # -e:1:in `<main>'
         # ------------------
         # --- Caused by: ---
         # NoMethodError:
         #   undefined method `action_links' for #<Chouette::TimeTable:0x007fc8cefb8260>
         #   ./app/views/time_tables/show.html.slim:13:in `block in _app_views_time_tables_show_html_slim__2702796193816469913_70250218141540'

      2) /time_tables/show should render a link to edit the time_table
         Failure/Error: - @time_table.action_links.each do |link|

         ActionView::Template::Error:
           undefined method `action_links' for #<Chouette::TimeTable:0x007fc8cb65b148>
         # ./app/views/time_tables/show.html.slim:13:in `block in _app_views_time_tables_show_html_slim__2702796193816469913_70250218141540'
         # ./app/helpers/newapplication_helper.rb:246:in `block (2 levels) in pageheader'
         # ./app/helpers/newapplication_helper.rb:244:in `block in pageheader'
         # ./app/helpers/newapplication_helper.rb:243:in `pageheader'
         # ./app/views/time_tables/show.html.slim:4:in `_app_views_time_tables_show_html_slim__2702796193816469913_70250218141540'
         # ./spec/views/time_tables/show.html.erb_spec.rb:20:in `block (2 levels) in <top (required)>'
         # -e:1:in `<main>'
         # ------------------
         # --- Caused by: ---
         # NoMethodError:
         #   undefined method `action_links' for #<Chouette::TimeTable:0x007fc8cb65b148>
         #   ./app/views/time_tables/show.html.slim:13:in `block in _app_views_time_tables_show_html_slim__2702796193816469913_70250218141540'

      3) /time_tables/show should render a link to remove the time_table
         Failure/Error: - @time_table.action_links.each do |link|

         ActionView::Template::Error:
           undefined method `action_links' for #<Chouette::TimeTable:0x007fc8cd251820>
         # ./app/views/time_tables/show.html.slim:13:in `block in _app_views_time_tables_show_html_slim__2702796193816469913_70250218141540'
         # ./app/helpers/newapplication_helper.rb:246:in `block (2 levels) in pageheader'
         # ./app/helpers/newapplication_helper.rb:244:in `block in pageheader'
         # ./app/helpers/newapplication_helper.rb:243:in `pageheader'
         # ./app/views/time_tables/show.html.slim:4:in `_app_views_time_tables_show_html_slim__2702796193816469913_70250218141540'
         # ./spec/views/time_tables/show.html.erb_spec.rb:25:in `block (2 levels) in <top (required)>'
         # -e:1:in `<main>'
         # ------------------
         # --- Caused by: ---
         # NoMethodError:
         #   undefined method `action_links' for #<Chouette::TimeTable:0x007fc8cd251820>
         #   ./app/views/time_tables/show.html.slim:13:in `block in _app_views_time_tables_show_html_slim__2702796193816469913_70250218141540'

    Finished in 2.44 seconds (files took 0.82818 seconds to load)
    3 examples, 3 failures

    Failed examples:

    rspec ./spec/views/time_tables/show.html.erb_spec.rb:14 # /time_tables/show should render h2 with the time_table comment
    rspec ./spec/views/time_tables/show.html.erb_spec.rb:19 # /time_tables/show should render a link to edit the time_table
    rspec ./spec/views/time_tables/show.html.erb_spec.rb:24 # /time_tables/show should render a link to remove the time_table

To match the controller, we need to decorate the `time_table` objects
used in these tests as well, because the view code has changed.
Decoration is necessary to give us the `#action_links` method that we
use to render the header links on the page.

Refs #3479