add ffi to Gemfile
add ffi to Gemfile

Change-Id: If859be8662babec75b2c237be32fa9a0da2c7a4b
Reviewed-on: https://gerrit.instructure.com/13418
Reviewed-by: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
Reviewed-by: Brian Palmer <3cb4e1df5ec4da2c7c4af7c52cec8cf340a55a10@instructure.com>
Tested-by: Zach Wily <9de8c4480303b5335cd2a33eefe814615ba3612a@instructure.com>

roxolan/canvas-lms,Rvor/canvas-lms,utkarshx/canvas-lms,ShreniiNepal/shrenii_lmp,grahamb/canvas-lms,utkarshx/canvas-lms,instructure/canvas-lms,juoni/canvas-lms,wye0220/shindig-canvas,instructure/canvas-lms,nditech/red-innovadores-lms,djbender/canvas-lms,ankithbti/canvas_lms,djbender/canvas-lms,Rvor/canvas-lms,wrdsb/canvas-lms,sli7246/canvas_branch,SwinburneOnline/canvas-lms,Jyaasa/canvas-lms,arrivu/qibla-ecampus,usmschuck/canvas,rup/Tarrax,wimemx/Canvas,shidao-fm/canvas-lms,roxolan/canvas-lms,venturehive/canvas-lms,loganrun/pincan,tgroshon/canvas-lms,wimemx/Canvas,skmezanul/canvas-lms,arrivu/qibla-ecampus,arrivu/hoodemo,parbros/red-innovadores-lms,grahamb/canvas-lms,antoniuslin/canvas-lms,Rvor/canvas-lms,usmschuck/canvas,djbender/canvas-lms,snehakachroo1/LSI_replica,rup/Tarrax,icelab/canvas,redconfetti/canvas-lms,parbros/red-innovadores-lms,sfu/canvas-lms,sfu/canvas-lms,sli7246/canvas_branch,efrj/canvas-lms,ShreniiNepal/shrenii_lmp,arrivu/arrivu-lms,antoniuslin/canvas-lms,tgroshon/canvas-lms,eCNAP/CANVAS,samuels410/greatlakes-lms,arrivu/qibla-ecampus,Unow/canvas-lms,arrivu/jigsaw-lms,dgynn/canvas-lms,sdeleon28/canvas-lms,landonwilkins/canvas-lms,shidao-fm/canvas-lms,instructure/canvas-lms,eCNAP/CANVAS,sfu/canvas-lms,SwinburneOnline/canvas-lms,matematikk-mooc/canvas-lms,AndranikMarkosyan/lms,sfu/canvas-lms,loganrun/pincan,grahamb/canvas-lms,parbros/red-innovadores-lms,SwinburneOnline/canvas-lms,Unow/canvas-lms,ShreniiNepal/shrenii_lmp,nditech/red-innovadores-lms,HotChalk/canvas-lms,ShreniiNepal/shrenii_lmp,venturehive/canvas-lms,Jyaasa/canvas-lms,arrivu/jigsaw-lms,skmezanul/canvas-lms,leftplusrightllc/canvas-lms,greyhwndz/canvas-lms,efrj/canvas-lms,ankithbti/canvas_lms,Unow/ins,jay3126/canvas-lms,icelab/canvas,greyhwndz/canvas-lms,arrivu/arrivu-lms,va7map/canvas-lms,merichar/canvas-lms,va7map/canvas-lms,sfu/canvas-lms,nditech/red-innovadores-lms,whalejasmine/canvas-lms,Rvor/canvas-lms,whalejasmine/canvas-lms,arrivu/hoodemo,usmschuck/canvas,shidao-fm/canvas-lms,fronteerio/canvas-lms,arrivu/jigsaw-lms,usmschuck/canvas,AndranikMarkosyan/lms,jay3126/canvas-lms,leftplusrightllc/canvas-lms,snehakachroo1/LSI_replica,matematikk-mooc/canvas-lms,kyroskoh/canvas-lms,HotChalk/canvas-lms,HotChalk/canvas-lms,dgynn/canvas-lms,tgroshon/canvas-lms,jay3126/canvas-lms,arrivu/arrivu-lms,rup/Tarrax,sdeleon28/canvas-lms,Unow/canvas-lms,roxolan/canvas-lms,fronteerio/canvas-lms,Unow/ins,arrivu/hiring-site,venturehive/canvas-lms,Unow/ins,gbleydon/canvas-lms,skmezanul/canvas-lms,antoniuslin/canvas-lms,samuels410/greatlakes-lms,kyroskoh/canvas-lms,samuels410/greatlakes-lms,djbender/canvas-lms,snehakachroo1/LSI_replica,fronteerio/canvas-lms,kyroskoh/canvas-lms,leftplusrightllc/canvas-lms,dgynn/canvas-lms,arrivu/hoodemo,matematikk-mooc/canvas-lms,instructure/canvas-lms,arrivu/hiring-site,skmezanul/canvas-lms,roxolan/canvas-lms,dgynn/canvas-lms,redconfetti/canvas-lms,va7map/canvas-lms,instructure/canvas-lms,efrj/canvas-lms,whalejasmine/canvas-lms,Jyaasa/canvas-lms,sli7246/canvas_branch,nditech/red-innovadores-lms,sfu/canvas-lms,landonwilkins/canvas-lms,AndranikMarkosyan/lms,snehakachroo1/LSI_replica,juoni/canvas-lms,shidao-fm/canvas-lms,wrdsb/canvas-lms,loganrun/pincan,sdeleon28/canvas-lms,narigone/canvas,landonwilkins/canvas-lms,grahamb/canvas-lms,ankithbti/canvas_lms,wrdsb/canvas-lms,sfu/canvas-lms,samuels410/greatlakes-lms,gbleydon/canvas-lms,wye0220/shindig-canvas,merichar/canvas-lms,utkarshx/canvas-lms,fronteerio/canvas-lms,AndranikMarkosyan/lms,eCNAP/CANVAS,greyhwndz/canvas-lms,juoni/canvas-lms,sdeleon28/canvas-lms,leftplusrightllc/canvas-lms,tgroshon/canvas-lms,Jyaasa/canvas-lms,narigone/canvas,efrj/canvas-lms,landonwilkins/canvas-lms,HotChalk/canvas-lms,wye0220/shindig-canvas,instructure/canvas-lms,instructure/canvas-lms,kyroskoh/canvas-lms,jay3126/canvas-lms,antoniuslin/canvas-lms,redconfetti/canvas-lms,icelab/canvas,eCNAP/CANVAS,wrdsb/canvas-lms,gbleydon/canvas-lms,va7map/canvas-lms,narigone/canvas,venturehive/canvas-lms,merichar/canvas-lms,juoni/canvas-lms,grahamb/canvas-lms,whalejasmine/canvas-lms,utkarshx/canvas-lms,greyhwndz/canvas-lms,matematikk-mooc/canvas-lms,narigone/canvas,arrivu/hiring-site,SwinburneOnline/canvas-lms,redconfetti/canvas-lms,wimemx/Canvas