Open the shirt size links in a new tab without destroying the partly filled form.

Fixes issue 1488.
diff --git a/app/soc/models/profile.py b/app/soc/models/profile.py
index dd747dd..6c64716 100644
--- a/app/soc/models/profile.py
+++ b/app/soc/models/profile.py
@@ -402,8 +402,8 @@
       choices=('XXS', 'XS', 'S', 'M', 'L', 'XL', 'XXL', 'XXXL'))
   tshirt_size.group = ugettext("4. Private Info")
   tshirt_size.help_text = ugettext('See also '
-      '<a href="http://bit.ly/ayGxJk"> for women</a> and '
-      '<a href="http://bit.ly/8ZrywF">for men</a>.')
+      '<a href="http://bit.ly/ayGxJk" target="_blank"> for women</a> and '
+      '<a href="http://bit.ly/8ZrywF" target="_blank">for men</a>.')
 
   #: Optional field indicating gender;
   #: kept private.