remove refresh-props! and update-props!
time travel support for ref cursors, test
0.8.0-alpha1
document public reference cursor api, om.core/root-cursor,
om.core/ref-cursor, and om.core/observe
ref cursor optimization - when no components depend on a path remove the
entry from _refs
update README
make om.core/ref-cursor idempotent
typo
sync up