Improve phoenix.new with Mix.shell.cmd/2 and error handling (#1785)
Improve phoenix.new with Mix.shell.cmd/2 and error handling (#1785)

* Use Mix.shell.cmd/2 instead of :os.cmd/1 because it now supports a quiet option

* Add error handling to command execution in case one fails

korobkov/phoenix,evax/phoenix,bsmr-erlang/phoenix,mobileoverlord/phoenix,trarbr/phoenix,nshafer/phoenix,bsmr-erlang/phoenix,stevedomin/phoenix,wsmoak/phoenix,michalmuskala/phoenix,Gazler/phoenix,CultivateHQ/phoenix,optikfluffel/phoenix,phoenixframework/phoenix,keathley/phoenix,trarbr/phoenix,ericmj/phoenix,phoenixframework/phoenix,0x00evil/phoenix,iStefo/phoenix,optikfluffel/phoenix,eksperimental/phoenix,jamilabreu/phoenix,iStefo/phoenix,CultivateHQ/phoenix,rafbgarcia/phoenix,wsmoak/phoenix,ybur-yug/phoenix,michalmuskala/phoenix,eksperimental/phoenix,phoenixframework/phoenix,rafbgarcia/phoenix,cas27/phoenix,nshafer/phoenix,Gazler/phoenix,ephe-meral/phoenix,dmarkow/phoenix,ericmj/phoenix,pap/phoenix,jwarwick/phoenix,Joe-noh/phoenix,jwarwick/phoenix,mschae/phoenix,stevedomin/phoenix,0x00evil/phoenix,ybur-yug/phoenix,jamilabreu/phoenix,gjaldon/phoenix,mobileoverlord/phoenix,dmarkow/phoenix,Ben-Evolently/phoenix,korobkov/phoenix,Joe-noh/phoenix,rafbgarcia/phoenix,nshafer/phoenix,pap/phoenix,gjaldon/phoenix,Kosmas/phoenix,optikfluffel/phoenix,evax/phoenix,mschae/phoenix,mitchellhenke/phoenix,0x00evil/phoenix,keathley/phoenix,Kosmas/phoenix,mitchellhenke/phoenix,ephe-meral/phoenix,cas27/phoenix