ENYO-455: Set explicit version of chai.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>
Merge pull request #926 from enyojs/ENYO-455-aarontam

ENYO-455: Set explicit version of chai.

Reviewed-By: Blake Stephens (blake.stephens@lge.com)
Integrated-By: Ryan Duffy (ryan.duffy@lge.com)