Features:
- Converts milestones/tickets/comments/labels
- Converts Trac usernames to Github usernames
- Sets assignees if possible, sets you an assignee otherwise
- Supports manual splitting of conversion process into stages
- Slows down to match the 60 requests per second API limit rate

Usage:
1. Copy config.php.sample to config.php and edit the configuration variables
2. Run it from shell, e.g.:
$ php trac2github.php