ENH: remove .apply in predict_transport_mode

[bifbof]

Just a small PR I came around to do.

• replaced an .apply that assigns categories based on speed with the pd.cut function. This complicates the code a bit, but not that much. Moves basically all computation to pandas
• removed an error if the input dictionary isn't sorted and instead just sort the input.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (495443f) 93.30% compared to head (d55f398) 93.32%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #596 +/- ## ========================================== + Coverage 93.30% 93.32% +0.01% ========================================== Files 33 33 Lines 2076 2067 -9 Branches 368 364 -4 ========================================== - Hits 1937 1929 -8 Misses 127 127 + Partials 12 11 -1 ```

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