Missing data for multi-select fields

Problem/Motivation

If a webform contains a select field with multiple options it is not possible to have this data sent over to Drupal.
It would be good if the data could be extracted so it can be sent up.

Steps to reproduce

1. Create a webform
2. Add a select field and configure it will unlimited options
3. Add the sfweb2lead_webform submission hook & configure the select field
4. Enable debug to help
5. Fill in the form and test

Proposed resolution

Update the current code so that it can work with multi-select fields and simply converts them to be inline strings.

Remaining tasks

Create patch and upload it.