Implement pure css solution to conversation fix.
Implement pure css solution to conversation fix.

fixes #8684

This fixes text from overflowing when using a
smaller screen.

test plan:
  * Click on inbox
  * Send a message to someone
  * In the conversations box to the left view message
  * Resize the screen to be below 800px
  * The conversation message should not overflow into other messages

Change-Id: I2c3a8a12e5b16f1eb244cd4626ad44f59ace6090
Reviewed-on: https://gerrit.instructure.com/13253
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Zach Pendleton <514dbb4d54d4f29e454990df7d075678f43f92aa@instructure.com>

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