TextPropertyManager should not update deleted components.
TextPropertyManager should not update deleted components.

Fixes #66.

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