sup-sync: error msg on :update
Merge #300: sup-tweak-labels sync back unless specified otherwise

Squashed commit of the following:

commit ebfb3335070bba8e27551dcc4c232a4de2e98044
Author: Wael M. Nasreddine <wael.nasreddine@gmail.com>
Date:   Wed Apr 30 22:26:10 2014 -0700

    sup-tweak-labels: add a newline before the begin

commit f1d51d3961b0864c5f05f7b728cf5dd722a967eb
Author: Wael M. Nasreddine <wael.nasreddine@gmail.com>
Date:   Wed Apr 30 22:22:23 2014 -0700

    sup-tweak-labels: sync_back (honor the settings global and source) and provide an override

commit c43319a5fdfb725455beda51b7ec08799ecdda89
Author: Wael M. Nasreddine <wael.nasreddine@gmail.com>
Date:   Tue Apr 29 15:54:01 2014 -0700

    sup-tweak-labels: sync back if specified