travis: add python3.5-dev for Pillow
travis: add python3.5-dev for Pillow

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