Use toBeCloseTo for javascript numbers.

5280 is the precise number of days between these two dates
as currently implemented.

Between
  1st of Jan 2000 23:59 and 16th of June 2014 00:00 -> 5280
  1st of Jan 2000 00:00 and 16th of June 2014 23:59 -> 5281.999...8

Related to issue #54.