Update arel dependency to version 2.1.5
Update arel dependency to version 2.1.5

voyera/adopt-a-hydrant,eebbesen/adopt-a-tree,voyera/adopt-a-hydrant,friendlycode/adopt-a-hydrant,baraka101/dar-adopt-a-mtaro,jasnow/adopt-a-hydrant,code4sac/adopt-a-light,OpenTwinCities/adopt-a-tree,Bryanprz/adopt-a-street,codefornigeria/adopt-a-hydrant,codeforanchorage/adopt-a-hydrant,siruguri/adopt-a-drain,Stackato-Apps/adopt-a-hydrant,codeforamerica/adopt-a-siren,openoakland/adopt-a-drain,friendlycode/adopt-a-hydrant,openshift-quickstart/adopt-a-hydrant-openshift-quickstart,0111001101111010/adopt-a-spot-odu,OpenTwinCities/adopt-a-tree,baraka101/dar-adopt-a-mtaro,HackMichiana/adopt-a-bus-stop,openoakland/adopt-a-drain,jamiekelly/adopt-a-hydrant,siruguri/adopt-a-drain,codeforamerica/adopt-a-hydrant,t-pfaff/adopt-a-hydrant,mapmeld/Adopt-a-Siren-Macon,voyera/adopt-a-hydrant,0111001101111010/adopt-a-spot-odu,codeforsavannah/adopt-a-garden,eebbesen/adopt-a-tree,friendlycode/adopt-a-hydrant,openshift-quickstart/adopt-a-hydrant-openshift-quickstart,baraka101/dar-adopt-a-mtaro,jasnow/adopt-a-hydrant,Stackato-Apps/adopt-a-hydrant,billyfung/van-racks,OpenTwinCities/adopt-a-tree,Stackato-Apps/adopt-a-hydrant,akintoey/adopt-a-hydrant,Bryanprz/adopt-a-street,codeforboston/adopt-a-hydrant,Bryanprz/adopt-a-street,t-pfaff/adopt-a-hydrant,billyfung/van-racks,eebbesen/adopt-a-tree,codeforsavannah/adopt-a-garden,codeforanchorage/adopt-a-hydrant,billyfung/van-racks,CostantinB/adopt-a-hydrant,codeforboston/adopt-a-hydrant,akintoey/adopt-a-hydrant,jamiekelly/adopt-a-hydrant,openshift-quickstart/adopt-a-hydrant-openshift-quickstart,CostantinB/adopt-a-hydrant,siruguri/adopt-a-drain,codeforamerica/adopt-a-hydrant,code4sac/adopt-a-light,t-pfaff/adopt-a-hydrant,codefornigeria/adopt-a-hydrant,jasnow/adopt-a-hydrant,codeforamerica/adopt-a-hydrant,codeforamerica/adopt-a-siren,HackMichiana/adopt-a-bus-stop,mapmeld/Adopt-a-Siren-Macon,akintoey/adopt-a-hydrant,CostantinB/adopt-a-hydrant,codefornigeria/adopt-a-hydrant,jamiekelly/adopt-a-hydrant,OpenTwinCities/adopt-a-tree