upgrade base images for php-fpm and workspace.

These duplicated Dockerfiles will be merged onto single Dockerfile
later. The same Dockerfile will check for the PHP version variable
and install the necessary softwar's accordingly.

php-fpm/Dockerfile-71

@@ -10,7 +10,7 @@
 #    https://hub.docker.com/r/laradock/php-fpm/tags/
 #
 
-FROM laradock/php-fpm:7.1--1.4
+FROM laradock/php-fpm:1.4-v7.1
 
 MAINTAINER Mahmoud Zalt <mahmoud@zalt.me>