ENH: Add install_from_ppa pillar setting and PPA pkgrepo

Synchronized upstart script with the one recommended by nginx.

http://wiki.nginx.org/Upstart

Fixes #39.

This reverts commit f6ba9ddb59.

the nginx.ng formula is only compatible with the upcoming feature
release, as noted here:

https://github.com/saltstack-formulas/nginx-formula#nginxng

This argument is only currently available in develop, and thus does not
belong in this formula at this time.

Support http_realip module

Create /var/log/nginx before running mkfifo

Add tab completion for upstart

Optionally include nginx.users via a pillar value

Fixes missing requisites in ng.init

If upstart is used, add symlink: /etc/init.d/nginx -> /lib/init/upstart-job

Added map file to resolve apache utils package name

Feature/misc config items

set 'daemon on;' by default

Fix errors in source.sls

fix link to formula usage instructions

Fixed minor typo in nginx.ng.config.sls

Context parameter safety fixes

Tightened up some ng requisites.