Update configuration.md
Update configuration.md

It seems that enabling proxy stops my instance from accepting local pushes, but I can't find mention of that in the docs.

Signed-off-by: Jason Freidman <68c46a606457643eab92053c1c05574abb26f861@periscope.io>

londoncalling/docker.github.io,spacexnice/distribution,denverdino/denverdino.github.io,moxiegirl/distribution,hopkings2008/distribution,jzwlqx/distribution,thaJeztah/docker.github.io,docker-zh/docker.github.io,docker/docker.github.io,joeuo/docker.github.io,liubin/distribution,menglingwei/denverdino.github.io,aprajshekhar/distribution,konstruktoid/distribution,xiekeyang/distribution,LuisBosquez/docker.github.io,hopkings2008/distribution,pdevine/distribution,runcom/distribution,konnase/distribution,miminar/distribution,jonboulle/distribution,aduermael/docker.github.io,joeuo/docker.github.io,aduermael/docker.github.io,xiekeyang/distribution,mikebrow/distribution,denverdino/denverdino.github.io,BSWANG/denverdino.github.io,vdemeester/distribution,jzwlqx/denverdino.github.io,BSWANG/denverdino.github.io,JimGalasyn/docker.github.io,sergeyfd/distribution,aaronlehmann/distribution,anweiss/docker.github.io,cyli/distribution,shin-/docker.github.io,troy0820/docker.github.io,dmcgowan/distribution,BSWANG/denverdino.github.io,andrewnguyen/distribution,LuisBosquez/docker.github.io,alexisbellido/docker.github.io,shubheksha/docker.github.io,JimGalasyn/docker.github.io,troy0820/docker.github.io,docker-zh/docker.github.io,joaofnfernandes/docker.github.io,menglingwei/denverdino.github.io,gdevillele/docker.github.io,sanscontext/docker.github.io,harrisonfeng/distribution,joaofnfernandes/docker.github.io,londoncalling/docker.github.io,anweiss/docker.github.io,miminar/distribution,phiroict/docker,mbentley/distribution,huamai-io/distribution,denverdino/docker.github.io,docker/distribution,duglin/distribution,johnstep/docker.github.io,gdevillele/docker.github.io,dobril-stanga/distribution,RyanDeng/distribution,johnstep/docker.github.io,manoj535/distribution,johnstep/docker.github.io,shubheksha/docker.github.io,BrianBland/distribution,thaJeztah/docker.github.io,RichardScothern/distribution,estesp/distribution,alexisbellido/docker.github.io,alexisbellido/docker.github.io,bdwill/docker.github.io,docker-zh/docker.github.io,troy0820/docker.github.io,JimGalasyn/docker.github.io,BrickXu/distribution,johnstep/docker.github.io,shubheksha/docker.github.io,bdwill/docker.github.io,liubin/distribution,nwt/distribution,phiroict/docker,stevvooe/distribution,joaofnfernandes/docker.github.io,docker-zh/docker.github.io,shin-/docker.github.io,LuisBosquez/docker.github.io,danix800/docker.github.io,danix800/docker.github.io,duglin/distribution,sebrandon1/distribution,sanscontext/docker.github.io,cezarsa/distribution,endophage/distribution,denverdino/distribution,shubheksha/docker.github.io,londoncalling/docker.github.io,jzwlqx/denverdino.github.io,vdemeester/distribution,schu/distribution,deis/distribution,docker/docker.github.io,shin-/docker.github.io,jzwlqx/distribution,rillig/docker.github.io,jwhonce/distribution,yuwaMSFT2/distribution,docker/docker.github.io,dmcgowan/distribution,cezarsa/distribution,denverdino/denverdino.github.io,nevermosby/distribution,RyanDeng/distribution,schu/distribution,manoj535/distribution,runcom/distribution,phiroict/docker,sanscontext/docker.github.io,denverdino/docker.github.io,danix800/docker.github.io,estesp/distribution,mikebrow/distribution,sanscontext/docker.github.io,jwhonce/distribution,jlhawn/distribution,thaJeztah/docker.github.io,gdevillele/docker.github.io,alexisbellido/docker.github.io,spacexnice/distribution,docker/distribution,mattrgreen/distribution,pdevine/distribution,LuisBosquez/docker.github.io,rillig/docker.github.io,menglingwei/denverdino.github.io,shyr/distribution,rbarlow/distribution,denverdino/denverdino.github.io,BSWANG/denverdino.github.io,menglingwei/denverdino.github.io,genedock/distribution,gdevillele/docker.github.io,deis/distribution,RichardScothern/distribution,jonboulle/distribution,joeuo/docker.github.io,kmala/distribution,jlhawn/distribution,anweiss/docker.github.io,Seb-Solon/distribution,JimGalasyn/docker.github.io,aaronlehmann/distribution,aduermael/docker.github.io,BrianBland/distribution,joeuo/docker.github.io,huamai-io/distribution,andrewnguyen/distribution,denverdino/distribution,aprajshekhar/distribution,noxiouz/distribution,sadlil/distribution,johnstep/docker.github.io,BSWANG/denverdino.github.io,moxiegirl/distribution,konstruktoid/distribution,genedock/distribution,sebrandon1/distribution,londoncalling/docker.github.io,mbentley/distribution,denverdino/docker.github.io,thaJeztah/distribution,troy0820/docker.github.io,djenriquez/distribution,konnase/distribution,bdwill/docker.github.io,endophage/distribution,gdevillele/docker.github.io,denverdino/distribution-stevvooe,thaJeztah/docker.github.io,BrickXu/distribution,thaJeztah/docker.github.io,mattrgreen/distribution,harrisonfeng/distribution,joeuo/docker.github.io,dobril-stanga/distribution,denverdino/docker.github.io,phiroict/docker,shin-/docker.github.io,shyr/distribution,cyli/distribution,anweiss/docker.github.io,shubheksha/docker.github.io,djenriquez/distribution,LuisBosquez/docker.github.io,Seb-Solon/distribution,sergeyfd/distribution,kmala/distribution,denverdino/docker.github.io,docker/docker.github.io,joaofnfernandes/docker.github.io,rbarlow/distribution,stevvooe/distribution,sanscontext/docker.github.io,alexisbellido/docker.github.io,shin-/docker.github.io,thaJeztah/distribution,jzwlqx/denverdino.github.io,danix800/docker.github.io,aduermael/docker.github.io,londoncalling/docker.github.io,phiroict/docker,sadlil/distribution,menglingwei/denverdino.github.io,jzwlqx/denverdino.github.io,nevermosby/distribution,bdwill/docker.github.io,jzwlqx/denverdino.github.io,joaofnfernandes/docker.github.io,denverdino/denverdino.github.io,docker/docker.github.io,bdwill/docker.github.io,noxiouz/distribution,denverdino/distribution-stevvooe,docker-zh/docker.github.io,JimGalasyn/docker.github.io,anweiss/docker.github.io,rillig/docker.github.io,nwt/distribution,rillig/docker.github.io,yuwaMSFT2/distribution