[Merge] lp:~pskoli93/postorius/Add-a-single-member into lp:postorius

[Pavan Koli]

> I believe your strings (in your error messages and the success message) need
> fixing to prep them for translation.
Made the required changes. Also used function ugettext() instead of gettext() for translations.
 Referring(https://docs.djangoproject.com/en/1.8/topics/i18n/translation/#standard-translation).
-- 
https://code.launchpad.net/~pskoli93/postorius/Add-a-single-member/+merge/256440
Your team Mailman Coders is requested to review the proposed merge of lp:~pskoli93/postorius/Add-a-single-member into lp:postorius.