remove unused Array#to and Array#from from lib/ext

Change-Id: Id59daa2c9e64833e8d843ebb55312faa5b5dcd0e
Reviewed-on: https://gerrit.instructure.com/30032
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Zach Pendleton <zachp@instructure.com>
Product-Review: Zach Pendleton <zachp@instructure.com>
QA-Review: Stephan Hagemann <stephan@pivotallabs.com>