Testing for years with 53 weeks (in ISO)

Added test for the 71 years in current 400-year cycle that have 53 weeks in ISO standard.

Based on a table taken from http://en.wikipedia.org/wiki/ISO_week_date (as downloaded on 2014-01-06) listing the 71 years in a 400-year cycle that have 53 weeks; in this case reflecting the 2000 based cycle.

Testing whether Dec 31 of these known years have an `isoWeek()` that equals 53.