Remove date from aggregated contributions.

If date is not defined, don't display it.
Hey @tdooner and @mikeubell ,
So I do think that the *footnote below should be enough to tell the user what is up BUT it is not. A smart reporter already came to the quick conclusion themselves that the figure represents the number of contributions not the money - so I had to correct him. 

Mike's Suggestion: Percentage of amount of itemized contributions from Oakland*

My header suggestion: Percentage of itemized contribution $ from Oakland*

I think you get the point across in the header which is important for those users that neglect the * and don't scroll down below all the candidates to see what that column means. And @tdooner I totally get it not wanting to add more words but maybe this gets the point across while still being a quite short header.

What do you think? @tdooner @mikeubell @elinaru @KyleW