Interpolate and upload 15 minute CSVs to API

Rather than relying on a Django management command, interpolate and
upload the CSVs from inside this app, using the new writeable surge
prediction endpoint.

https://www.pivotaltracker.com/story/show/80543482
[Delivers #80543482]
Merge pull request #13 from sealevelresearch/bring-in-import-surge-functionality

Interpolate and upload 15 minute CSVs to API