'organizes multiple extensions that are separated with commas or
passed by using --extension/-e multiple times.
for example: running \'django-admin compress -e js,txt -e xhtml -a\'
would result in an extension list: [\'.js\', \'.txt\', \'.xhtml\']
>>> handle_extensions([\'.html\', \'html,js,py,py,py,.py\', \'py,.py\'])
[\'.html\', \'.js\']
>>> handle_extensions([\'.html, txt,.tpl\'])
[\'.html\', \'.tpl\', \'.txt\']'

def handle_extensions(self, extensions=(u'html',)):

    ext_list = []
    for ext in extensions:
        ext_list.extend(ext.replace(u'    ', u'').split(u','))
    for (i, ext) in enumerate(ext_list):
        if (not ext.startswith(u'.')):
            ext_list[i] = (u'.%s' % ext_list[i])
    return set(ext_list)
