[#75] Fixed incorrect configuration for `discovery.ec2.group`

Fixing issue with AWS plugin, attribute for security group should be discovery.ec2.group
[#75] Fixed incorrect handling of the "elasticsearch-cloud-aws" plugin

The "elasticsearch-cloud-aws" plugin can't be named just "aws" in the plugin attributes,
as the plugin recipe will tries to install it, and fail,
causing Elasticsearch to restart on every Chef run.
[#75] Upgrade the "elasticsearch-cloud-aws" plugin to 1.11.0
[#75] Improve the installation of the Fog gem

* Force installation of packages required for the Fog gem before the Chef run
* Use `run_action` for the Fog gem
[#75] Fixing `nil` for discovery_tags.each
[#75] Removed unneccessary code for `node.elasticsearch.discovery.ec2.tag`

Related: #66
[#75] Need to rescue the data attribute as it will be nil if your not using that recipe (like in dev)
[#75] Do not use `rescue` for `data['devices']` in `attributes/data.rb`

Revert "[#75] Need to rescue the data attribute as it will be nil if your not using that recipe (like in dev)"

This should not be needed:

    data = raise('BAM') rescue {}

    setting = data['devices'] || {}

    p setting

This reverts commit 45eb5ec133b28390c52c6c4437c964167b9fd350.
[FIX] Do not install the "aws" plugin if the node does not have the "aws" recipe

Closes #76
Add a "health check" page for the Nginx proxy, usable in ELB/etc

If you set the `node.elasticsearch.nginx.allow_status` attribute to `true`,
Nginx will allow un-authenticated requests to `/status`, returning
the response from `curl -i localhost:9200` (a `HEAD` request).

Closes #70
Release 0.2.6
Update the `rake release` task
[#78] Use verbose resource name for `mount` in recipes/data

Fixes <http://acrmp.github.com/foodcritic/#FC022>
[#78] Remove unneccessary interpolation in elasticsearch-env.sh.erb template

Fixes <http://acrmp.github.com/foodcritic/#FC002>
[#78] Prefer `not_if` instead of Ruby `unless` condition in recipes/proxy

Fixes <http://acrmp.github.com/foodcritic/#FC023>

-----

Note by @karmi: This Foodcritic rule is actually quite dubious, as stated on the site.
                But for the sake of static code analysis gods, why not.
Use `Chef::Log.debug` instead of `STDOUT.print` in recipes/proxy
Update Gemfile to reflect changes in Bundler

Use explicit `source`
Fix incorrect names for packages in recipes/ebs

Use `value_for_platform` to with platform-specific package names for libxslt and libxml

Closes #77
[#77] Simplify recipes/ebs code to use `value_for_platform_family`
[#77] Added `build-essential` into Vagrantfile and recipes/ebs

NOTE: Even though the "build-essential" cookbook is included in the node `run_list`,
`build-essential` is not installed and `make` is not available before the Chef run,
making the installation of the Fog gem fail.

That's why we need to include the build-essential/make/gcc/etc packages also in the
`value_for_platform_family` in recipes/ebs.