Alpine image is huge

[mbrevda]

The alpine based image, merged in #176, is about 28% smaller than the original, which is good. An image built using the alpine package manager is 96% smaller than the original! Accordingly, and as per @ncopa (who wrote the pr for alpine), there is still some work to be done that can bring the image size down.

php                   alpine              e40e7aabdb36        17 hours ago        376.5 MB
php                   latest              8c8eb06f7c64        17 hours ago        483.8 MB
frolvlad/alpine-php   latest              9eda42b8cf2e        2 weeks ago         18.22 MB

[ncopa]

see #206

[mbrevda]

Tracked in #206, thanks!