Update documentation for module

Added the new options to the example configuration file and added some
notes for the new configuration options:

- address: Select which address of the instance you want to use as the
  host address, or the address that Shinken will use to access it
- use_tags: EC2 tags that should be used as templates. The default is
  'use' and the format of the template names should be key:value. This
  allows us to use more than one template per host, and additional
  flexibility.

Also added documentation for 'regions' since it wasn't present at the,
though it works.
Update documentation for module

Added the new options to the example configuration file and added some
notes for the new configuration options:

- address: Select which address of the instance you want to use as the
  host address, or the address that Shinken will use to access it
- use_tags: EC2 tags that should be used as templates. The default is
  'use' and the format of the template names should be key:value. This
  allows us to use more than one template per host, and additional
  flexibility.

Also added documentation for 'regions' since it wasn't present at the,
though it works.