Create binding to download Foreman resources

## Need

```gherkin
As a developer
I want to download a Foreman instance resources as JSON objects
So that I can  describe the instance as a Git repository
```

## Deliverables

- A binding to make API calls to the Foreman instance and download the resources as JSON objects.
The objects will be dumped as files in the Git repository via the ConfigurationManager #6 
- The binding will be used by the synchronization cron (ran by the Foregit daemon) or via a command from CLI.
- The repository structure should be configured via a setting, to describe which resource should be downloaded in which directory and the file name formats.

## Solution

#### Prerequisites
- apipie-bindings - use it to make API calls to download the resources


#### TODO
- [x] create Foreman::Download class to make API calls to download the resources:
  - create a list of resources which will be downloaded: architesures, hosts_groups, OSs
  - for each resource make API calls to download them, and call the ConfigManager class to save them as files 

#### Files
-  lib/foreman/download.rb

The problem with Ruby 1.9.3 is that it returns 'nil' here, instead of the hash. you might either not using the OpenStruct and returning the hash here, or returning the Settings object here, calling `SETTINGS.resources` instead of `SETTINGS[:resources]` or returning directly `YAML.load(File.read(settings_path))`