v0.3.3 - update to tract version 0.12.4

ONNX-ML decision trees (e. g. exported from LightGBM or XGBoost) are now supported! 🎉
See the demo here.

Commits:

• fix version location 01c4577
• add tree demo 4f9c2e9
• update cypress 3fc0bb1
• update readme 28b3992
• download test models from backblaze 4e7a0c8
• update to tract 12.2, more exhaustive DatumType matching 8f5468b
• v0.3.2 2252423

Commit Range:
v0.3.2...master