Bug Fixes and add Multiple Authors Improvements

* Fix absolute rather paths created bug in the extension xml
* Fix Magento connect bug with missing file by adding a blank note in the contents
* Fix the unnecessary extra 'value' node
* Add multiple authors simply by adding comma delimited name, user, and email in the extension-config.php file
Merge pull request #15 from rgabruel/fix_bugs_and_add_ability_to_add_multiple_authors

Bug Fixes and add Multiple Authors Improvements