Handle dayOfWeek+dayOfMonth the same as vixiecron

    crontab(5) says
    > The day of a command's execution can be specified by two fields -
    > day of
    > month, and day of week. If both fields are restricted (ie, aren't
    > *),
    > the command will be run when either field matches the current
    > time.

    The current behaviour is to require both fields to match.
Switch from cabal-dev to cabal-install sandboxes

This requires cabal >= 1.18
Ensure all dates in the diff-day test are valid
Only use match-one behaviour if neither DaySpec is a star
Added a testcase for weekday&monthday restriction
Fixed duplicated field typo
Merge pull request #8 from joelwilliamson/master

Handle dayOfWeek+dayOfMonth the same as vixiecron