Removed unused rigidSizing option
Removed headers rereating upon resizing

Rationale: if user wants to append custom elements (like resize icon) into
.rc-handler class after calling $('table').resizableColumns(), recreating them
will make it disappear.
Added option to synchronize handlers upon resizing

Rationale: better support for .rc-handler user CSS stylesheets. If user adds an
icon or custom background for grips, it won't get "stuck" during resizing
anymore. Controlled with "syncHandlers" option, defaults to true.