Converted due_date_select to axios

app/assets/javascripts/due_date_select.js

 /* global dateFormat */
 
 import Pikaday from 'pikaday';
+import axios from './lib/utils/axios_utils';
 import { parsePikadayDate, pikadayToString } from './lib/utils/datefix';
 
 class DueDateSelect {
@@ -125,12 +126,6 @@ class DueDateSelect {
   }
 
   submitSelectedDate(isDropdown) {
-    return $.ajax({
-      type: 'PUT',
-      url: this.issueUpdateURL,
-      data: this.datePayload,
-      dataType: 'json',
-      beforeSend: () => {
     const selectedDateValue = this.datePayload[this.abilityName].due_date;
     const displayedDateStyle = this.displayedDate !== 'No due date' ? 'bold' : 'no-value';
 
@@ -145,11 +140,10 @@ class DueDateSelect {
     this.$valueContent.html(`<span class='${displayedDateStyle}'>${this.displayedDate}</span>`);
     this.$sidebarValue.html(this.displayedDate);
 
-        return selectedDateValue.length ?
-          $('.js-remove-due-date-holder').removeClass('hidden') :
-          $('.js-remove-due-date-holder').addClass('hidden');
-      },
-    }).done(() => {
+    $('.js-remove-due-date-holder').toggleClass('hidden', selectedDateValue.length);
+
+    return axios.put(this.issueUpdateURL, this.datePayload)
+      .then(() => {
         if (isDropdown) {
           this.$dropdown.trigger('loaded.gl.dropdown');
           this.$dropdown.dropdown('toggle');