i18nliner(.rb)

this swaps out (most of) our ruby haax with i18nliner

test plan:
1. verify string extraction:
   1. `rake i18n:generate` before and after this commit
   2. confirm `config/locales/generated/en.yml` is identical
2. verify english defaults:
   1. use canvas in english
   2. confirm everything looks correct
3. verify translation keys/scopes:
   1. run canvas w/ RAILS_LOAD_ALL_LOCALES=true and optimized js
   2. use canvas in spanish
   3. confirm that todo está bien
4. confirm you can now use i18nliner-y features:
   1. call `t` without a key
   2. use the fancy erb block syntax

Change-Id: I979479c0889fe7e31ee0c962a4bd1998ab54d711
Reviewed-on: https://gerrit.instructure.com/42785
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jennifer Stern <jstern@instructure.com>
Product-Review: Jennifer Stern <jstern@instructure.com>
QA-Review: Matt Fairbourn <mfairbourn@instructure.com>