Remove date from aggregated contributions.

If date is not defined, don't display it.
I could go with either one below.  It is hard to mistake what the $ means.

> On Sep 7, 2014, at 3:13 PM, lla2105 <notifications@github.com> wrote:
> 
> In views/index.haml:
> 
> > @@ -57,7 +57,7 @@
> >                      <th id='mayoral-table-name-column'></th>
> >                      <th class='mayoral-table-head bold'>Total Raised</th>
> >                      <th class='mayoral-table-head'>Number of itemized contributions</th>
> > -                    <th class='mayoral-table-head'>Percentage of itemized contributions from Oakland*</th>
> > +                    <th class='mayoral-table-head'>Percentage of amount of itemized contributions from Oakland*</th>
> 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
> 
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