Use correct datetime format for import_predictions

eg `2014-08-03T12:00:00Z` instead of `2014-08-03T12:00:00+00:00`

[#80649322]
Load field `predicted_tide_level`

Rather than `predicted_height`

https://www.pivotaltracker.com/story/show/80649322 [Fixes #80649322]
Merge pull request #97 from sealevelresearch/import-predictions-datetime-format

Use correct CSV format for import_predictions