Missing Source Mapping in webcomponents-lite.js

[Manifold0]

Running directly from the github repository:

gem 'polymer-rails', github: "alchaplinsky/polymer-rails", branch: "master"

GIT
  remote: https://github.com/alchaplinsky/polymer-rails.git
  revision: b6b0940bb8ed70e092b560414ce9d65531f850ed
  branch: master
  specs:
    polymer-rails (2.0)
      nokogiri (~> 1.6)
      nokogumbo (= 1.4.2)
      rails (>= 3.1.0)
      sprockets (~> 3.0)

Rails 5.1.4 Ruby 2.3.1

//# sourceMappingURL=webcomponents-lite.js.map

Refers to a file that is not in the gem, leading to a routing error:

ActionController::RoutingError (No route matches [GET] "/assets/webcomponentsjs/webcomponents-lite.js.map")

I've run into some other issues when attempting to use the webcomponents-loader.js in my application.js so I've dropped down to pointing directly at lite:

//= require webcomponentsjs/webcomponents-lite

.js removed, as per sewalliniusm's ticket #96