typo fix in installation doc
typo fix in installation doc

mortenwh/django-userena,ugoertz/django-userena,RDXT/django-userena,bread-and-pepper/django-userena,bread-and-pepper/django-userena,mortenwh/django-userena,RDXT/django-userena,bioinformatics-ua/django-userena,ugoertz/django-userena,bopo/django-userena,bioinformatics-ua/django-userena,bopo/django-userena,pyghassen/django-userena,bioinformatics-ua/django-userena,pyghassen/django-userena,ugoertz/django-userena,mortenwh/django-userena,bread-and-pepper/django-userena,pyghassen/django-userena,RDXT/django-userena