make sure sprockets gets cleared out when done

lib/flowerbox/runner/base.rb

@@ -95,6 +95,8 @@ module Flowerbox
               raise RunnerDiedError.new if attempts == 0
 
               Flowerbox.server = nil
+            ensure
+              @sprockets.reset!
             end
           end
 

lib/flowerbox/sprockets_handler.rb

@@ -69,6 +69,10 @@ module Flowerbox
 
       raise LogicalPathNotFoundError.new("Could not find logical path for #{asset_path}")
     end
+
+    def reset!
+      @environment.send(:expire_index!)
+    end
   end
 end