Merge pull request #6 from catherinev/pair-rickytux,catherinev

there should actually be new tests this time...
add mark_as_complete! and mark_as_incomplete! methods, allow @status to be complete
Merge pull request #7 from catherinev/pair-kimpossibleg,monicadev

add mark_as_complete! and mark_as_incomplete! methods, allow @status to ...
added completed? tests