Fix: Do not round bbox coordinates in mode opendatacam-darknet

Merge pull request opendatacam#13 from opendatacam/mot

Evo: Benchmark compatibility with MOT challenge + Add opendatacam/darknet compat

Evo: turning keeping all history in memory optional opendatacam#11

Evo: add probability score from YOLO in the tracker output

Evo: release 0.5 with zombie status in output