Add Pie Chart For Energy Use by Type

[vkoves]

All energy uses are in a standard unit (kBTU) and so we should be able to easily show how much energy a building gets from each source, like so:

It might be worth getting feedback on whether this is useful, but I think it's good to show off if a building has low usage in some areas that's offset by, say, high district heat use.

[vkoves]

We added D3 with some other graphs, which makes this a lot easier, and makes the data easier to understand

[vkoves]

This was resolved in PR #116! 🎉