Adopt `binderhub` #127

Job	Run time
Build tljh_repo2docker	1m 16s
Unit tests (3.8)	11m 49s
Integration tests (local)	1m 38s
Unit tests (3.9)	17m 6s
Integration tests (binderhub)	1m 26s
Isolated tests	31s
Unit tests (3.10)	16m 26s
	50m 12s

Provide feedback