fix to work with new api changes in enyo.Control
need to temporarily switch this to be opt-in
Updated comment to reflect opt-in nature of useFlex flag.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>
Merge pull request #89 from enyojs/fix-sampler

Fix to work with new internal changes in enyo.Control

Looks good!

Reviewed-by: Aaron Tam (aaron.tam@lge.com)