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
Add support for time-shifting

So we can have a secondary port, time-shifted from our primary port.

https://www.pivotaltracker.com/story/show/80544126
[Delivers #80544126]
Merge pull request #14 from sealevelresearch/support-time-shifting

Add support for time-shifting
Skip files already loaded

Otherwise we try and load *every* file on *every* run.

[Delivers #81149930]
Merge pull request #15 from sealevelresearch/skip-already-loaded

Skip files already loaded
Tests to demonstrate parsing bug

[#81113902]