make Rails 3 the default
make Rails 3 the default

Rails2 support still available by env var or config/RAILS2

Change-Id: I127105dfd3d3bef19e51a2c7fc53b64748115625
Reviewed-on: https://gerrit.instructure.com/37471
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: James Williams  <3a5f4ed991dbfa5c9ef76ad729d240ca12f62180@instructure.com>
Product-Review: Bryan Madsen <0a3ba1af216659500dd8f41e29f3979f42452870@instructure.com>
QA-Review: Bryan Madsen <0a3ba1af216659500dd8f41e29f3979f42452870@instructure.com>

va7map/canvas-lms,redconfetti/canvas-lms,leftplusrightllc/canvas-lms,greyhwndz/canvas-lms,matematikk-mooc/canvas-lms,redconfetti/canvas-lms,eCNAP/CANVAS,djbender/canvas-lms,grahamb/canvas-lms,greyhwndz/canvas-lms,samuels410/greatlakes-lms,wrdsb/canvas-lms,narigone/canvas,efrj/canvas-lms,sfu/canvas-lms,dgynn/canvas-lms,snehakachroo1/LSI_replica,utkarshx/canvas-lms,HotChalk/canvas-lms,instructure/canvas-lms,sdeleon28/canvas-lms,Rvor/canvas-lms,tgroshon/canvas-lms,whalejasmine/canvas-lms,shidao-fm/canvas-lms,roxolan/canvas-lms,narigone/canvas,matematikk-mooc/canvas-lms,gbleydon/canvas-lms,grahamb/canvas-lms,roxolan/canvas-lms,kyroskoh/canvas-lms,va7map/canvas-lms,juoni/canvas-lms,tgroshon/canvas-lms,efrj/canvas-lms,kyroskoh/canvas-lms,Unow/canvas-lms,utkarshx/canvas-lms,venturehive/canvas-lms,skmezanul/canvas-lms,snehakachroo1/LSI_replica,grahamb/canvas-lms,wrdsb/canvas-lms,roxolan/canvas-lms,Rvor/canvas-lms,wye0220/shindig-canvas,jay3126/canvas-lms,narigone/canvas,juoni/canvas-lms,skmezanul/canvas-lms,djbender/canvas-lms,narigone/canvas,matematikk-mooc/canvas-lms,venturehive/canvas-lms,whalejasmine/canvas-lms,dgynn/canvas-lms,leftplusrightllc/canvas-lms,AndranikMarkosyan/lms,samuels410/greatlakes-lms,sdeleon28/canvas-lms,HotChalk/canvas-lms,instructure/canvas-lms,SwinburneOnline/canvas-lms,djbender/canvas-lms,Rvor/canvas-lms,Rvor/canvas-lms,ShreniiNepal/shrenii_lmp,instructure/canvas-lms,djbender/canvas-lms,redconfetti/canvas-lms,wye0220/shindig-canvas,grahamb/canvas-lms,instructure/canvas-lms,snehakachroo1/LSI_replica,whalejasmine/canvas-lms,sfu/canvas-lms,leftplusrightllc/canvas-lms,instructure/canvas-lms,tgroshon/canvas-lms,venturehive/canvas-lms,ShreniiNepal/shrenii_lmp,shidao-fm/canvas-lms,sfu/canvas-lms,va7map/canvas-lms,Jyaasa/canvas-lms,samuels410/greatlakes-lms,dgynn/canvas-lms,antoniuslin/canvas-lms,antoniuslin/canvas-lms,greyhwndz/canvas-lms,juoni/canvas-lms,roxolan/canvas-lms,va7map/canvas-lms,fronteerio/canvas-lms,antoniuslin/canvas-lms,tgroshon/canvas-lms,dgynn/canvas-lms,fronteerio/canvas-lms,efrj/canvas-lms,shidao-fm/canvas-lms,wye0220/shindig-canvas,kyroskoh/canvas-lms,shidao-fm/canvas-lms,ShreniiNepal/shrenii_lmp,sfu/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,jay3126/canvas-lms,skmezanul/canvas-lms,sfu/canvas-lms,fronteerio/canvas-lms,matematikk-mooc/canvas-lms,utkarshx/canvas-lms,leftplusrightllc/canvas-lms,Unow/canvas-lms,eCNAP/CANVAS,juoni/canvas-lms,sdeleon28/canvas-lms,redconfetti/canvas-lms,utkarshx/canvas-lms,kyroskoh/canvas-lms,skmezanul/canvas-lms,efrj/canvas-lms,SwinburneOnline/canvas-lms,AndranikMarkosyan/lms,antoniuslin/canvas-lms,AndranikMarkosyan/lms,Unow/canvas-lms,whalejasmine/canvas-lms,HotChalk/canvas-lms,gbleydon/canvas-lms,eCNAP/CANVAS,jay3126/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,wrdsb/canvas-lms,fronteerio/canvas-lms,snehakachroo1/LSI_replica,ShreniiNepal/shrenii_lmp,greyhwndz/canvas-lms,samuels410/greatlakes-lms,SwinburneOnline/canvas-lms,wrdsb/canvas-lms,instructure/canvas-lms,Jyaasa/canvas-lms,jay3126/canvas-lms,sdeleon28/canvas-lms,venturehive/canvas-lms,Jyaasa/canvas-lms,Jyaasa/canvas-lms,AndranikMarkosyan/lms,SwinburneOnline/canvas-lms,gbleydon/canvas-lms,eCNAP/CANVAS,HotChalk/canvas-lms