remove use of dict comprehensions to retain python 2.6 support
    
    Dict comprehensions (PEP-274) were added to python 2.7+. The patch that added the --mine
    option to list-tasks made use of a dict comprehension, which broke python 2.6 support.
    This patch restores the older dict() + list comprehension approach, which restores
    support for python 2.6.