Replace "avg of itemized contribs" column with "$ left"

[evanwolf]

1. The $/contributor number was interesting early on.
2. With some campaigns raising from relatively few contributors, the mean-big-contribution figures are a bit misleading. For instance, they don't exclude self-funding.
3. it's the last month of the election. Who has spent everything? Who will we hear from in the last week?

[elinaru]

I agree that the "Available Balance" is probably more interesting now than "Average of itemized contributions" at this point. Although, I do like that finding this number requires users to drill into individual candidate pages—which offers more info than what's presented on the homepage.

If we do replace the last column of the main candidates table with available balances, let's be sure to move the Average of itemized contributions to the individual candidate pages, so we're still offering that number somewhere.