updated sampler to better UX when showcasing showPercentages
Merge pull request #1834 from enyojs/ENYO-641-derekanderson

ENYO-641: Slider: Turning Off and On Percentage erases Negative Values

Reviewed-By: Ryan Duffy (ryan.duffy@lge.com)
Integrated-By: Aaron Tam (aaron.tam@lge.com)