Tests created differ, probably due to Dict order

[joto]

Every time I create the tests data using create_test_data.py I get a different mvt file. I believe this is because before Python 3.6 dictionaries are not ordered.

This is probably the problematic place:
https://github.com/mapbox/vector-tile-base/blob/vt3/tests/create_test_data.py#L137-L151

[joto]

Same problem in a few other places. Also in create_valid_single_layer_v2_linestring for instance.