Pull latest image tag, so we can identity it

`docker image ls` doesn't tell us what the latest deployed image is (e.g
if we've rolled back). Pull the latest image tag through to the server
so we can use it instead.

lib/mrsk/commands/app.rb

@@ -87,19 +87,6 @@ class Mrsk::Commands::App < Mrsk::Commands::Base
       "tail -n 1"
   end
 
-  def most_recent_version_from_available_images
-    pipe \
-      docker(:image, :ls, "--format", '"{{.Tag}}"', config.repository),
-      "head -n 1"
-  end
-
-  def all_versions_from_available_containers
-    pipe \
-      docker(:image, :ls, "--format", '"{{.Tag}}"', config.repository),
-      "head -n 1"
-  end
-
-
   def list_containers
     docker :container, :ls, "--all", *filter_args
   end

lib/mrsk/commands/builder/base.rb

@@ -7,6 +7,7 @@ class Mrsk::Commands::Builder::Base < Mrsk::Commands::Base
 
   def pull
     docker :pull, config.absolute_image
+    docker :pull, config.latest_image
   end
 
   def build_options