Adopt `binderhub` #140

Job	Run time
Build tljh_repo2docker	1m 28s
Isolated tests	36s
Unit tests (3.8)	37m 32s
Integration tests (local)	8m 46s
Integration tests (binderhub)	8m 16s
Unit tests (3.9)	36m 10s
Unit tests (3.10)	36m 5s
	2h 8m 53s

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