- Require long options to be at least 2 chars long, only allow alphanume...

- Require long options to be at least 2 chars long, only allow alphanumeric as first char (don't allow dash/underscore as first char)
- Check for duplicate short/long options and throw InvalidArgumentException if a duplicate is found
- Duplicate option checking is only done if the $allowDuplicates param in __construct is set to FALSE (default)
- Updated @version phpdoc tags (version & modified date)