Fix frontend email regex for login page.

Currently we are using Django 1.4 regex for email validation which
does not allow custom domains (e.g. eclo.solutions), fixed it with
latest Django 1.11 regex.

LEARNER-2828

common/static/common/js/utils/edx.utils.validate.js

@@ -103,12 +103,12 @@
                         },
 
                         email: {
-                        // This is the same regex used to validate email addresses in Django 1.4
+                        // This is the same regex used to validate email addresses in Django 1.11
                             regex: new RegExp(
                             [
                                 '(^[-!#$%&\'*+/=?^_`{}|~0-9A-Z]+(\\.[-!#$%&\'*+/=?^_`{}|~0-9A-Z]+)*',
                                 '|^"([\\001-\\010\\013\\014\\016-\\037!#-\\[\\]-\\177]|\\\\[\\001-\\011\\013\\014\\016-\\177])*"', // eslint-disable-line max-len
-                                ')@((?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\\.)+[A-Z]{2,6}\\.?$)',
+                                ')@((?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\\.)+)(?:[A-Z0-9-]{2,63})',
                                 '|\\[(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)(\\.(25[0-5]|2[0-4]\\d|[0-1]?\\d?\\d)){3}\\]$'
                             ].join(''), 'i'
                         ),