Instead of installing a keymap that overrides orgmode commands, use a sparse
keymap only on nroam sections.
nroam.el (nroam-sections-map): New keymap for nroam sections.
(with-nroam-markers): Put the new keymap in an overlay on nroam sections.
(nroam-ctrl-c-ctrl-c): Remove unused function.
(nroam-return):
(nroam-update): Do not fallback to org commands anymore.
Instead of installing a keymap that overrides orgmode commands, use a sparse keymap only on nroam sections.