Return an error (other than 0) when ./hugo fails
Return an error (other than 0) when ./hugo fails

Being a good OS citizen so folks can compose hugo into their tool chain.
Also helps with git bisect run.

MarkDBlackwell/hugo,Zenithar/hugo,mdhender/hugo,vbatoufflet/hugo,gohugoio/hugo,tischda/hugo,soundrussian/hugo,coderzh/hugo,ryanclarke/hugo,badoet/hugo,bramp/hugo,mitchchn/hugo,fhergomez/hugo,bramp/hugo,anthonyfok/hugo,jygastaud/hugo,abourget/hugo,gohugoio/hugo,anthonyfok/hugo,tischda/hugo,mdhender/hugo,tubo028/hugo,ryanclarke/hugo,fedelibre/hugo,Zenithar/hugo,derekperkins/hugo,tatsushid/hugo,sprig/hugo,tjyang/hugo,jygastaud/hugo,vbatoufflet/hugo,ifraixedes/hugo,mdhender/hugo,derekperkins/hugo,anthonyfok/hugo,fedelibre/hugo,ffrizzo/hugo,tjyang/hugo,mayah/hugo,gohugoio/hugo,melo/hugo,MarkDBlackwell/hugo,bogem/hugo,melo/hugo,badoet/hugo,digitalcraftsman/hugo,mayah/hugo,tatsushid/hugo,ffrizzo/hugo,sprig/hugo,ifraixedes/hugo,mitchchn/hugo,mdhender/hugo,digitalcraftsman/hugo,soundrussian/hugo,coderzh/hugo,bogem/hugo,abourget/hugo,fhergomez/hugo,kujohn/hugo,halostatue/hugo,halostatue/hugo,fedelibre/hugo,tubo028/hugo,kujohn/hugo,fedelibre/hugo