message: Use encoded download URL for MFR URL
  build fileURL from config.OSF.url and guid instead of window.location
  build mfrUrl from config.OSF.renderUrl instead of hard-coded
diff: @@ -2,6 +2,8 @@ import Component from '@ember/component';
  import { computed } from '@ember/object';
  import { htmlSafe } from '@ember/string';
  import Analytics from 'ember-osf/mixins/analytics';
  +import config from 'ember-get-config';
  +import pathJoin from 'ember-osf/utils/path-join';
  export default Component.extend(Analytics, {
  // -- Component arguments -- //
  @@ -24,7 +26,7 @@ export default Component.extend(Analytics, {
  }),
  fileUrl: computed('file', function() {
  - return encodeURIComponent(window.location.href);
  + return encodeURIComponent(pathJoin(config.OSF.url, this.get('file.guid')));
  }),
  twitterUrl: computed('file.name', 'fileUrl', function() {
  @@ -44,7 +46,8 @@ export default Component.extend(Analytics, {
  }),
  mfrUrl: computed('file', function() {
  - return `https://mfr.osf.io/render?url=${window.location.href}?action=download%26mode=render`;
  + const encodedDownloadUrl = encodeURIComponent(pathJoin(config.OSF.url, this.get('file.guid'), 'download'));
  + return `${config.OSF.renderUrl}?url=${encodedDownloadUrl}`;
  }),
  shareiFrameDynamic: computed('mfrUrl', function() {
  