highlight discussion tab as active on discussions#index
highlight discussion tab as active on discussions#index

test plan:
make sure the discussions tab in the left nav bar 
is highlighted with a blue background when you’re 
on the Discussions page.  

Change-Id: Ib34337dcf579fbcc6a81fe87b39bf9f3966dd3b0
Reviewed-on: https://gerrit.instructure.com/13164
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Ryan Florence <2d8900489f91ac272fd9ce9d5789db6522668ca2@instructure.com>

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