MDL-55835 eslint: bump to v3.7.1

1) Bump eslint verson in npm
2) Enable tabs rule introduced in 3.2.0
3) With rules deprecated in 3.3.0 to their replacements
   http://eslint.org/blog/2016/08/eslint-v3.3.0-released
4) Deprecate the use of M.str (fixes MDLSITE-3646) with new
   no-restricted-properties introduced in 3.5.0
5) Fixup no-unused-vars - remove argsIgnorePattern which shouldn't have allowed
   partial matches and turns out to be uncesssary
   (detected because of https://github.com/eslint/eslint/issues/7250 in 3.6.0)

lib/amd/src/str.js

@@ -24,6 +24,8 @@
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  * @since      2.9
  */
+// Disable no-restriced-properties because M.str is expected here:
+/* eslint-disable no-restricted-properties */
 define(['jquery', 'core/ajax', 'core/localstorage'], function($, ajax, storage) {