View previous contributions

[spengrah]

Contributor can see their previous contributions within a round

View can see recipient contribution totals from previous rounds

[xuhcc]

can see recipient contribution totals from previous rounds

Implemented along with #25

Contributor can see their previous contributions within a round

Already done (cart remains open throughout the round).

But we also show cart from previous round when user navigates to it (#25). This allows users to see their past contributions. Possible improvements:

• Do not save every change to local storage after contributing. Only update saved cart when user actually reallocates funds.
• Do not allow to change cart after the end of the round.
• Do not allow to add projects to cart after the end of the round.