Added `Access-Control-Allow-Headers` in the Nginx proxy configuration

See elasticsearch/elasticsearch#2186.
Added correct HTTP headers for cross-origin Ajax into Nginx proxy config

Tested with the following code opened from `file://` location and from an HTML page at different domain then myserver.com:

    jQuery.ajax({ url: "http://myserver.com/_search",
                  type: "POST",
                  contentType: 'application/json; charset=UTF-8',
                  success: function(data) { console.log(data)}
    });

See elasticsearch/elasticsearch#2186.
Changed, that minimum and maximum memory (-Xms and -Xmx) are set to the same value

See <http://www.elasticsearch.org/guide/reference/setup/installation.html>

Closes #35.
Restructured the `attributes.rb` file

Also, removed `index_shards` and `index_replicas` settings -- better set them via API
for each index you create.
Improve repeatability of the "increase limits for the elasticsearch user" step

Note: Still not fully idempotent, will just add, not update the file, when values change.
Make use of Berkshelf Vagrant integration, default distro is Precise

Thanks to the Berkshelf [Vagrant integration](http://berkshelf.com/#vagrant_with_berkshelf),
the cookbooks are automatically downloaded and mounted inside the virtual machine,
allowing to skip the step of installing them manually.

Readme updated to convey this information, added explicit require to Vagrantfile

Also, default to the `precise64` virtual machine.
Added "activesupport" to Gemfile

So we can do `bundle exec vagrant up`
Allow to install a specific Chef version via the omnibus installer

To install the latest Chef version, launch the virtual machine with a command like this:

    CHEF=true vagrant up precise64

To install a specific version, launch it like this:

    CHEF=10.12.0 vagrant up precise64

Uses the Vagrant `shell` provisioner (you can specify multiple provisioners in one Vagrantfile)
Remove dependency on Nginx cookbook and use a custom recipe to install it

The [community Nginx cookbook](https://github.com/opscode-cookbooks/nginx)
is effectively FUBAR.

It brings in a dependency on the `bluepill` cookbook, which itself is absolutely FUBAR.
It is not idempotent when installing via source, it is unneccesarily complex,
and keeps breaking all the time.

So a lightweight (43 LOC), custom recipe is used (`recipes/nginx.rb`),
simple configuration files are stored in `templates`.

The `elasticsearch::proxy_nginx` recipe automatically pulls in the `elasticsearch::proxy_nginx`;
if you need more modularity and controll, please submit an issue.

Closes #24, fixes #30.
Renamed the `elasticsearch::proxy_nginx` recipe to simple `elasticsearch::proxy`
Check if the `monitrc` resource exists

Other Monit cookbooks exists, such as <https://github.com/axsuul/cookbook-monit>,
which don't have the `monitrc` resource, so let's be strict about this.

Closes #34.
Make sure the init script returns proper exit codes
[DOC] Remove curly quotes in README (fixes `InvalidByteSequenceError`)

Some quotation marks were \xE2 instead of \x22, and broke the cookbook
upload in some environments. Let's use ASCII quotes then.

Closes #18
Update default elasticsearch version to 0.19.10
Updated the "elasticsearch-cloud-aws" plugin to 1.9.0 version
Release 0.0.3
Renamed the `elasticsearch::plugin_aws` recipe (et al.) to simple `elasticsearch::aws`
Refactored plugins installation to be more flexible

* A "elasticsearch::plugins" recipe was added to allow explicit control on plugin installation
* The recipe will install all plugins listed in a databag `elasticsearch/plugins` or `node.elasticsearch['plugins']` attribute
* Polish the `install_plugin` definition
Refactored plugin installation to work with specific versions or URLs

The `install_plugin` definition was refactored into an extension,
allowing more control -- it's a regular Ruby method.

See the `libraries/extensions.rb` for more info.

The plugin options should be set in data bags or node attributes -- example:

    { elasticsearch: {
        plugins: {
          'karmi/elasticsearch-paramedic' => {},
          'lukas-vlcek/bigdesk'           => { 'version' => '1.0.0' },
          'hunspell'                      => { 'url' => 'https://github.com/downloads/...' }
        }
      }
    }
Added the ability to set mandatory plugins

elasticsearch won't start without mandatory plugins present

Use `node.plugins_mandatory` to configure the array of mandatory plugins

The "elasticsearch::aws" recipe adds the `cloud-aws` plugin as mandatory automatically.