Adds 'bundle exec' to RACK_ENV command in contributing.md line 206
Adds 'bundle exec' to RACK_ENV command in contributing.md line 206

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Tonkpils/exercism.io,nathanbwright/exercism.io,jtigger/exercism.io,tejasbubane/exercism.io,tejasbubane/exercism.io,treiff/exercism.io,Tonkpils/exercism.io,mhelmetag/exercism.io,RaptorRCX/exercism.io,jtigger/exercism.io,mhelmetag/exercism.io,treiff/exercism.io,nathanbwright/exercism.io,treiff/exercism.io,nathanbwright/exercism.io,IanDCarroll/exercism.io,RaptorRCX/exercism.io,jtigger/exercism.io,treiff/exercism.io,mhelmetag/exercism.io,RaptorRCX/exercism.io,jtigger/exercism.io,IanDCarroll/exercism.io,IanDCarroll/exercism.io,nathanbwright/exercism.io,Tonkpils/exercism.io,mhelmetag/exercism.io,RaptorRCX/exercism.io,tejasbubane/exercism.io,IanDCarroll/exercism.io,tejasbubane/exercism.io,Tonkpils/exercism.io