Goss > Added build-time testing

Leveraging https://github.com/aelsabbahy/goss for serverspec -like validation during build phase.

Alpine: available as a separate build in mainline

Will be exposed on Docker Hub using -alpine tags, but majority of code (other than Dockerfile) is now shared between Ubuntu and Alpine builds.

Dockerfile: exposing unprivileged port number as ENV variable

Merge pull request #32 from bryanlatten/feature-port-env

Dockerfile: added unprivileged port to ENV variables (as constant)

Nginx: running on non-privileged port (8080)

BREAKING: Newer docker releases (1.11+) on certain platforms ship with updated default security profiles. These disable the existing capability addition trick, setcap, that previously allowed an unprivileged nginx user to bind to a privileged port (80). Instead, nginx now uses an unprivileged port (8080).

Run.d / Nginx reuse

Prevents duplicate symlink when re-running a tagged, 2-phase built container

S6: Leveraging trap function to propagate SIGQUIT on SIGTERM

Allow nginx to gracefully shutdown workers, instead of a hard stop

PID 1: Replaced Supervisor with S6

• microscopic size, 1MB
• no dependencies (compared with ~50MB for supervisor)
• moved most run.d functionality into S6-supported startup mechanism
• nginx master process no longer root

Ubuntu: unlocked point version 14.04

Merge pull request #23 from bryanlatten/feature-ubuntu-base

Dockerfile: revert to ubuntu

Nginx: unlocked stable version

Merge pull request #19 from bryanlatten/feature-nginx-patch

Dockerfile: unlocking nginx version

Rollup: all previous updates

Merge pull request #15 from bryanlatten/feature-dist-upgrade

Dockerfile: remove committed (outdated) versions