Fix build adding ppa:ondrej/php due to wrong locale
Fix build adding ppa:ondrej/php due to wrong locale

Builds are broken because `add-apt-repository` is not currently working properly for non-UTF-8 locales. As stated here (at the bottom): https://hub.docker.com/r/byrnedo/nginx-php7-fpm/builds/bzje4ek6czubarxtk8qw3aq/

This should fix it. (it worked for me locally)
byrnedo/docker-nginx-php7-fpm,byrnedo/docker-nginx-php7-fpm