CONTRIBUTING: add tips for succesful changes
CONTRIBUTING: add tips for succesful changes

Expand the contributing doc to include tips for successful PRs and
guidance on commit messages. This should help contributers to have
better position PRs that are more likely to be merged.

Signed-off-by: Stephen J Day <63efd86fa22882ae89b6027b22a36e4db1f4214d@docker.com>

qudongfang/docker,konstruktoid/docker-upstream,ibuildthecloud/docker,jlhawn/docker,djs55/docker,imkin/moby,Mokolea/docker,cpuguy83/docker,mike1729/docker,moby/moby,whuwxl/docker,dsheets/moby,dmcgowan/docker,pradipd/moby,gschaetz/moby,michael-holzheu/docker,darrenstahlmsft/moby,cpuguy83/docker,ripcurld0/moby,estesp/docker,mahak/docker,mtesselH/docker,liaoqingwei/docker,dims/docker,johnstep/moby-moby,charleszheng44/moby,kencochrane/docker,darrenstahlmsft/docker,Mokolea/docker,ibuildthecloud/docker,charleszheng44/moby,Syntaxide/docker,mstanleyjones/docker,tklauser/docker,thaJeztah/docker,diogomonica/docker,thaJeztah/docker,KingEmet/docker,konstruktoid/docker-1,diogomonica/docker,kencochrane/docker,raja-sami-10p/moby,coolljt0725/docker,laijs/docker,gjaskiewicz/moby,charleszheng44/moby,ibuildthecloud/docker,jlhawn/docker,kolyshkin/moby,madhanrm/docker,trebonian/docker,ndeloof/docker,x1022as/docker,PatrickLang/moby,imkin/moby,tklauser/docker,tklauser/docker,ndeloof/docker,darrenstahlmsft/moby,diogomonica/docker,lixiaobing1/docker,thtanaka/docker,tianon/docker,crosbymichael/docker,jwhonce/docker,nawawi/docker,erikstmartin/docker,raja-sami-10p/moby,moypray/docker,sdurrheimer/docker,paralin/docker,erikstmartin/docker,justincormack/docker,cyphar/docker,bearstech/moby,docker/docker,yasiramin10p/moby,liaoqingwei/docker,KingEmet/docker,KarthikNayak/docker,rremer/moby,Syntaxide/docker,johnstep/moby-moby,allencloud/docker,dperny/docker,miminar/docker,q384566678/docker,crosbymichael/docker,yosifkit/docker,gschaetz/moby,scotttlin/docker,estesp/docker,sdurrheimer/docker,nawawi/docker,moul/docker,shishir-a412ed/docker,KarthikNayak/docker,tophj-ibm/moby,ffoysal/docker,allencloud/docker,srust/docker,lixiaobing1/docker,noironetworks/docker,gnailuy/docker,bearstech/moby,dccurtis/docker,sarnautov/moby,yongtang/docker,Ramzec/docker,darrenstahlmsft/moby,shhsu/docker,gnailuy/docker,lixiaobing10051267/docker,whuwxl/docker,unclejack/docker,shishir-a412ed/docker,sarnautov/moby,dgageot/docker,jimjag/docker,flavio/docker,mkumatag/docker,laijs/moby,JMesser81/docker,miminar/docker,JMesser81/docker,YuPengZTE/docker,tianon/docker,trebonian/docker,gjaskiewicz/moby,flavio/docker,catinthesky/docker,Mokolea/docker,rremer/moby,ColinHebert/docker,amatsus/docker,dims/docker,srust/docker,jvanz/docker,AkihiroSuda/docker,yosifkit/docker,trebonian/docker,coolljt0725/docker,POLJM242/docker,pramodhkp/moby,fcrisciani/docker,alfred-landrum/docker,HideoYamauchi/docker,madhanrm/docker,pradipd/moby,thaJeztah/docker,PatrickLang/moby,YuPengZTE/docker,mixja/docker,SvenDowideit/docker,mstanleyjones/docker,ColinHebert/docker,kolyshkin/docker,AkihiroSuda/docker,djs55/docker,Ramzec/docker,thtanaka/docker,sterchelen/docker,kojiromike/docker,ibuildthecloud/docker,AkihiroSuda/docker,justincormack/docker,whuwxl/docker,cpuguy83/docker,crosbymichael/docker,fcrisciani/docker,bonczj/moby-json-file-logger,konstruktoid/docker-1,mike1729/docker,haveatry/docker,shhsu/docker,moul/docker,djs55/docker,paralin/docker,erikh/docker,miminar/docker,lixiaobing10051267/docker,qudongfang/docker,mikebrow/docker,xuxinkun/docker,yasiramin10p/moby,ffoysal/docker,mahak/docker,imkin/moby,yosifkit/docker,yongtang/docker,ndeloof/docker,coreos/docker,coreos/docker,AkihiroSuda/docker,jwhonce/docker,catinthesky/docker,haveatry/docker,xuxinkun/docker,nalind/docker,laijs/docker,catinthesky/docker,danyalKhaliq10p/moby,kojiromike/docker,HideoYamauchi/docker,cyphar/docker,flavio/docker,kolyshkin/moby,dims/docker,trebonian/docker,sarnautov/moby,vdemeester/docker,lixiaobing10051267/docker,estesp/docker,nawawi/docker,JMesser81/docker,tophj-ibm/moby,yasiramin10p/moby,danyalKhaliq10p/moby,jvanz/docker,mike1729/docker,mkumatag/docker,coreos/docker,YuPengZTE/docker,nalind/docker,tophj-ibm/docker,prertik/docker,akira-baruah/docker,sdurrheimer/docker,yummypeng/docker,tophj-ibm/docker,SvenDowideit/docker,mahak/docker,gschaetz/moby,vdemeester/docker,rancher/docker,jvanz/docker,rhatdan/docker,nawawi/docker,konstruktoid/docker-1,hqhq/moby,dgageot/docker,mikebrow/docker,jimjag/docker,bearstech/moby,michael-holzheu/docker,thtanaka/docker,alfred-landrum/docker,mikebrow/docker,allencloud/docker,shhsu/docker,q384566678/docker,cyphar/docker,jameszhan/docker,mixja/docker,konstruktoid/docker-upstream,resin-io/docker,dsheets/moby,tonistiigi/docker,amatsus/docker,yongtang/docker,unclejack/docker,qudongfang/docker,duglin/docker,mstanleyjones/docker,jimjag/docker,laijs/docker,vdemeester/docker,x1022as/docker,dperny/docker,bonczj/moby-json-file-logger,naveed-jamil-tenpearls/moby,tonistiigi/docker,scotttlin/docker,paralin/docker,raja-sami-10p/moby,shishir-a412ed/docker,prertik/docker,mtesselH/docker,unclejack/docker,erikstmartin/docker,mkumatag/docker,Syntaxide/docker,ripcurld0/moby,docker/docker,mahak/docker,laijs/moby,jlhawn/docker,KingEmet/docker,POLJM242/docker,dmcgowan/docker,yummypeng/docker,ColinHebert/docker,prertik/docker,dperny/docker,maxamillion/docker,yosifkit/docker,michael-holzheu/docker,darrenstahlmsft/docker,x1022as/docker,tmp6154/docker,sterchelen/docker,rhatdan/docker,flavio/docker,bearstech/moby,paralin/docker,HideoYamauchi/docker,liaoqingwei/docker,rremer/moby,nalind/docker,justincormack/docker,danyalKhaliq10p/moby,mixja/docker,dccurtis/docker,darrenstahlmsft/docker,noironetworks/docker,Mokolea/docker,kojiromike/docker,srust/docker,tmp6154/docker,jameszhan/docker,gnailuy/docker,hqhq/moby,duglin/docker,jthelin/docker,kolyshkin/moby,sterchelen/docker,moul/docker,tophj-ibm/moby,laijs/moby,rhatdan/docker,nalind/docker,ffoysal/docker,scotttlin/docker,mtesselH/docker,haveatry/docker,jwhonce/docker,akira-baruah/docker,ripcurld0/moby,rancher/docker,amatsus/docker,SvenDowideit/docker,moby/moby,noironetworks/docker,kencochrane/docker,jameszhan/docker,bonczj/moby-json-file-logger,cpuguy83/docker,thaJeztah/docker,dgageot/docker,resin-io/docker,jimjag/docker,moypray/docker,pramodhkp/moby,ibuildthecloud/docker,tophj-ibm/docker,dsheets/moby,dccurtis/docker,rancher/docker,gjaskiewicz/moby,madhanrm/docker,dmcgowan/docker,naveed-jamil-tenpearls/moby,erikh/docker,tmp6154/docker,resin-io/docker,johnstep/moby-moby,maxamillion/docker,moby/moby,tonistiigi/docker,jthelin/docker,konstruktoid/docker-upstream,q384566678/docker,naveed-jamil-tenpearls/moby,fcrisciani/docker,hqhq/moby,moul/docker,duglin/docker,alfred-landrum/docker,moby/moby,moypray/docker,gnailuy/docker,kolyshkin/docker,pramodhkp/moby,erikh/docker,coolljt0725/docker,docker/docker,Ramzec/docker,PatrickLang/moby,Ramzec/docker,maxamillion/docker,lixiaobing1/docker,pradipd/moby,konstruktoid/docker-upstream,xuxinkun/docker,KarthikNayak/docker,yummypeng/docker