rehydrateFileList (items) {
    const fauxFileList = items.reduce((fileList, item) => {
      const key = this.options ? this.options.fileUrlKey : 'url'
      const url = item[key]
      const ext = (url && url.lastIndexOf('.') !== -1) ? url.substr(url.lastIndexOf('.') + 1) : false
      const mime = this.options.mimes[ext] || false
      fileList.push(Object.assign({}, item, url ? {
        name: item.name || url.substr((url.lastIndexOf('/') + 1) || 0),
        type: item.type ? item.type : mime,
        previewData: url
      } : {}))
      return fileList
    }, [])
    this.addFileList(fauxFileList)
    this.results = this.mapUUID(items)
  }
Given a pre-existing array of files, create a faux FileList.
@param {array} items expects an array of objects [{ url: '/uploads/file.pdf' }]
@param {string} pathKey the object-key to access the url (defaults to "url")