Add support to get the ISO-8601 numeric representation of the day of the week when using "N".
Fix leak of the getDayOfWeek function into the global scope.
Check explicitly dow === 0.
Merge pull request #9 from lbdremy/numeric_representation_of_the_day_of_the_week

Add support to get the ISO-8601 numeric representation of the day of the week when using "N"