Loading Global Configuration, Extending ENV Object, Empty Config File

Hi,

I added three important features.

1: Loading the global configuration too.
In this particular example, `developer_name` would now be loaded too.

``` yaml
# config/application.yaml
developer_name: "SeriousM"

development:
  database_server: "localhost"
```
Reason: there might some vars that are always the same eg. the developer's name.

2: Extending the ENV Object.
That means that configuration that was loaded should also be found in the ENV Object.
eg. `ENV['developer_name']` or `ENV['database_server']`

Reason: I have to reference to use the ENV object in the `config/mongoid.yml` file that looks the same for every developer but the `config/application.yml` changes.

3: No error occur when the file is empty.
Reason: In certain environments the environment variables are already set but you require that the file `config/application.yml` exists. Therefor i just drop the command `touch config/application.yml` to satisfy your requirements but the file is just empty.

I hope you'll like the changes.

Cheers