bump bluecloth for a version that install unders ruby 2.2

Change-Id: I820fafdcc98e66b59564bfd962bd3ac4f03973a5
Reviewed-on: https://gerrit.instructure.com/46320
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Rob Orton <rob@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>