> Proposed spec:
> '''
> Modify the API statistics.mode to handle multimodal cases so that the 
> first mode encountered is the one returned.  If the input is empty, 
> raise a StatisticsError.

Are you happy guaranteeing that it will always be the first mode 
encountered? I'm not happy about it, but I'll follow you lead on this 
one.

> TestCases:
>     mode([])   --> StatisticsError
>     mode('aabbbcc') --> 'c'

That should be 'b'.

>     mode(iter('aabbbcc')) --> 'c'

And again 'b'.

>     mode('eeffddddggaaaa') --> 'a'

If it is first encountered, that should be 'd'.