escape html chars in json in rails3

closes CNVS-11784

Change-Id: I4d86d11244ee32b46768c8d18431dc9e188e132b
Reviewed-on: https://gerrit.instructure.com/31755
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: Brian Palmer <brianp@instructure.com>
QA-Review: Brian Palmer <brianp@instructure.com>