Updated README to reference correct environmental variable.
Updated README to reference correct environmental variable.

SivagnanamCiena/marathon,gsantovena/marathon,HardikDR/marathon,sepiroth887/marathon,janisz/marathon,c089/marathon,gsantovena/marathon,sepiroth887/marathon,gsantovena/marathon,pugna0/marathon,lelezi/marathon,meln1k/marathon,airbnb/marathon,guenter/marathon,janisz/marathon,manojlds/marathon,SivagnanamCiena/marathon,Yhgenomics/marathon,airbnb/marathon,IanSaunders/marathon,hangyan/marathon,EvanKrall/marathon,sttts/marathon,murat-lacework/marathon,HardikDR/marathon,meln1k/marathon,gsantovena/marathon,HardikDR/marathon,mesosphere/marathon,EvanKrall/marathon,EasonYi/marathon,mesosphere/marathon,spacejam/marathon,mesosphere/marathon,EasonYi/marathon,matsluni/marathon,bobrik/marathon,Kosta-Github/marathon,sttts/marathon,felixb/marathon,bobrik/marathon,mikejihbe/marathon,c089/marathon,janisz/marathon,matsluni/marathon,guenter/marathon,sledigabel/marathon,IanSaunders/marathon,guenter/marathon,MrMarvin/marathon,pugna0/marathon,EasonYi/marathon,c089/marathon,drewrobb/marathon,hangyan/marathon,matsluni/marathon,quamilek/marathon,SivagnanamCiena/marathon,lelezi/marathon,meln1k/marathon,MrMarvin/marathon,spacejam/marathon,drewrobb/marathon,yp-engineering/marathon,airbnb/marathon,airbnb/marathon,titosand/marathon,timcharper/marathon,spacejam/marathon,mesosphere/marathon,c089/marathon,Caerostris/marathon,cherrydocker/marathon-1,Caerostris/marathon,felixb/marathon,rtward/marathon,MrMarvin/marathon,rtward/marathon,pgkelley4/marathon,ayouwei/marathon,cgvarela/marathon,ramitsurana/marathon,mikejihbe/marathon,okuryu/marathon,natemurthy/marathon,ramitsurana/marathon,cherrydocker/marathon-1,janisz/marathon,pgkelley4/marathon,Yhgenomics/marathon,sielaq/marathon,felixb/marathon,Kosta-Github/marathon,rtward/marathon,cgvarela/marathon,14Zen/marathon,vivekjuneja/marathon,janisz/marathon,natemurthy/marathon,guenter/marathon,cherrydocker/marathon-1,meln1k/marathon,sttts/marathon,EvanKrall/marathon,felixb/marathon,okuryu/marathon,sepiroth887/marathon,sledigabel/marathon,bsideup/marathon,murat-lacework/marathon,sielaq/marathon,manojlds/marathon,Yhgenomics/marathon,spacejam/marathon,ayouwei/marathon,ss75710541/marathon,mesosphere/marathon,drewrobb/marathon,14Zen/marathon,bsideup/marathon,cgvarela/marathon,guenter/marathon,Caerostris/marathon,Caerostris/marathon,14Zen/marathon,yp-engineering/marathon,quamilek/marathon,pugna0/marathon,meln1k/marathon,timcharper/marathon,titosand/marathon,bobrik/marathon,bsideup/marathon,gsantovena/marathon,hangyan/marathon,EvanKrall/marathon,IanSaunders/marathon,mikejihbe/marathon,manojlds/marathon,sttts/marathon,ss75710541/marathon,ayouwei/marathon,murat-lacework/marathon,sielaq/marathon,drewrobb/marathon,Caerostris/marathon,ramitsurana/marathon,sielaq/marathon,timcharper/marathon,ss75710541/marathon,sledigabel/marathon,14Zen/marathon,vivekjuneja/marathon,bobrik/marathon,quamilek/marathon,natemurthy/marathon,vivekjuneja/marathon,okuryu/marathon,lelezi/marathon