Merge pull request #28 from desec-io/20171020_devadmin_php5

fix(devadmin): enforce PHP 5

devadmin/Dockerfile

@@ -1,4 +1,4 @@
-FROM richarvey/nginx-php-fpm
+FROM richarvey/nginx-php-fpm:php5
 
 RUN apk add --no-cache \
 	php5-gettext \