Improve nginx.conf

Workers can be higher and Phabricator complains if we have invalid
paths in the config.
Update base image on build

This is so we don't need to fetch new packages every time
we `run` this Docker container.

We just need to update base packages in this container at build
time so we don't re-update every run.
Add APC support

opensuse is stuck on PHP 5.4, so we can't use the PHP 5.5 built
in opcode cache.  Until we use PHP 5.5 (or base all of this on
a different system), we can use APC directly here.

As of this commit, this entire image generates a _clean_ phabricator
install with no "unresolved setup issues" except for the base
case of "enable people to create accounts."
Merge pull request #2 from mattsta/add-apc-fix-paths

Improvements: Fix php-fpm path, update base image on build, include APC