New : Added composer.json

Added composer.json file which will help this module for submission on proposed extension.silverstripe.org website. Please add more fields according to requirements.

For more information please visit at http://extension.openbees.org/instructions/

Todo  :

1 -  you also need to add "extra" field for snapshot, like
```json
{
    ......... 
    "extra":
    {
        "snapshot" : "http://example.com/example.jpg"
    }
}
 ```

This will help us to showcase your module in "New Module" section.