ActionPack tests fixed

I should provide a little more info I suppose. The Duration class that
makes 1.year.ago and friends accurate broke the tests for DateHelper,
since the tests depended on the values generated by 1.year etc to be
wrong. The patch adjusts the ranges of the minutes that map to which
strings, rather than changing the tests to use to_f on the results of
1.year etc. If the latter approach is preferred, I'll whip up another
patch for it.

Applied. Thanks for staying on top of that.