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.

workspace/Dockerfile-71

@@ -11,7 +11,7 @@
 #
 
 # placeholder. Need change after new image would be built.
-FROM laradock/workspace:1.3
+FROM laradock/workspace:1.6
 
 MAINTAINER Mahmoud Zalt <mahmoud@zalt.me>