['search user'] select2: enable 'directly enter email'

* the separator is 'Enter', i.e., clicking the Enter key

static/scripts/common.js

@@ -538,8 +538,6 @@ define([
                 // tags need `<input type="hidden" />`, not `<select>`
                 tags: [],
 
-                tokenSeparators: [",", " "],
-
                 minimumInputLength: 1, // input at least 1 character
 
                 formatInputTooShort: gettext("Please enter 1 or more character"),
@@ -590,6 +588,13 @@ define([
                 formatSelection: function(item) {
                     return _this.HTMLescape(item.name || item.id); // if no name, show the email, i.e., when directly input, show the email
                 },
+
+                createSearchChoice: function(term) {
+                    return {
+                        'id': $.trim(term)
+                    };
+                },
+
                 escapeMarkup: function(m) { return m; }
             }
         },