Treat cursor as atomic.
Treat cursor as atomic.

Fixes #118

michael/substance-1,substance/substance,andene/substance,abhaga/substance,jacwright/substance,TypesetIO/substance,andene/substance,michael/substance-1,TypesetIO/substance,substance/substance,stencila/substance,abhaga/substance,podviaznikov/substance,jacwright/substance,podviaznikov/substance