prep for 0.13.0

Prep for 0.12 (econ-ark#176)

* lock requirements for 0.12 release

* update binder link for stable 0.12.0 release

increase nbval timeout

Merge pull request econ-ark#144 from sbenthall/sb-0.10.8b

fixes for 0.10.b

Merge pull request econ-ark#129 from MridulS/remove_figs

remove figures added to the DemARK repo

create a DemARK release for v0.10.5

PerfForesightCRRA-Impatience to QuARK

Convert Fagering_demos to Jupyter notebook

Auto adds Zotero library config for cite2c

Revert "ProofRead KS"