This Fixes #986 : added function to show year in dates

@gordonwoodhull , please review.
Subtle bug here, which can be seen on notebook 16837a758ec64be81dea on the internal deployment.  
(I can dig up a public github example if you don't have access.)

![image](https://cloud.githubusercontent.com/assets/1366709/4989956/c885d002-694e-11e4-9d65-568b3f90395a.png)

Since it's comparing the year with the adjacent history items, it will not show the year for these history items from 10/21 and 10/28 of last year.  The goal is to show the year for any entries not from *this* year, so even though it's asymmetrical, this should be using now instead of d2.