Nginx/Gunicorn support for RedHat and other small things

[squarebracket]

Changes from upstream:

• Nginx/Gunicorn is now fully supported on both Debian and RedHat-like systems
• The correct username/group is now used across apache/nginx for both Debian
  and RedHat
• Pip is now the default provider for Django to ensure mutually-working package
  versions are installed.
• Added initscripts for RedHat
• Added workaround for race condition bug in graphite
• Added configuration variable gr_web_server_remove_default -- default config is
  only wiped when the variable is true, or when it is undef and
  gr_web_server_port == 80
• Renamed gr_apache_port and gr_apache_port_https to gr_web_server_port and
  gr_web_server_port respectively. If the old configuration values are used, puppet
  throws an error telling you to use the new ones. (If you don't want to bump a major
  version number for these changes, I can change it to a deprecation warning, but
  that's less elegant.)
• Fixed resource chaining bug causing failure on Ubuntu 12.04.5
• Added Compatbility Notes to README

Changes since fork that are in line with latest commits:

• Default package versions of 0.9.15/1.5 for graphite/Django
• Twisted is explicitly installed before txamqp (more reliable than simply reordering)
• Added package python-tzlocal package for RedHat

To test the changes, I provisioned stock VMs with puppet and pip. I did two runs of
puppet apply per OS:

1. include graphite
2. class { 'graphite': gr_web_server => 'nginx', }

If I could display a metric in the Graphite Composer, then the test passed.

Now for all the caveats:

• CentOS 6/7 requires a symlink from /usr/bin/pip-python to /usr/bin/pip (see:
  PUP-3829 for CentOS 6/7))
• CentOS 7's default nginx.conf includes a server section listening on port 80.
  Thus, it is not possible to set up graphite without modifying the package-provided
  configuration file. I opted to do nothing about this; graphite will successfully,
  but the default server section has to be removed from nginx.conf. This needs
  to be noted somewhere in the README file.
• These tests were done with SELinux disabled.
• Debian is using the gunicorn-debian script, which calls gunicorn_django, which is deprecated.
• Everything should be using python-cairocffi now, as it's what is recommended/required by graphite. However, Ubuntu 15.10's python-cairocffi package is broken (it tries to important somelib.so when the actual file is somelib.so.1), so I've kept all debian variants using python-cairo.
• Ubuntu 15.10 requires a systemctl restart gunicorn after install

The following OS's were tested successfully:

• CentOS 6.7
• CentOS 7.2.1511
• Debian 7.9
• Debian 8.2
• Ubuntu 12.04.5
• Ubuntu 14.04.3
• Ubuntu 15.10

The following OS's did not work:

• Ubuntu 15.04
  The pip provider is broken (see PUP-4502

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Huh. Not sure why the tests are failing, as bundle exec rake validate && bundle exec rake lint && bundle exec rake spec SPEC_OPTS='--color --format documentation' for me only gives warnings about case statements missing defaults and that I'm missing the metadata-json-lint gem.

[dwerder]

We do not allow Warnings at the Linting part. So maybe you can add a Default to the case statements. Easiest way would be to just add something like:

   Default: {
     fail("$foobar is not supported.")
  }

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All the rspec tests are passing now, I've fixed up a couple things here and there, and added some notes to the README. I updated the top comment.

[dwerder]

Great commit. Thanks for the complete readme and the tests.

[dwerder]

Just one small last hint. Maybe you can add an axample for use of this module with nginx in the example section of the readme. Like this one: https://github.com/echocat/puppet-graphite#configuration-with-apache-24-and-cors

So its not necessary.