Make shasum the lowest priority checksum command.
Make shasum the lowest priority checksum command.

This fixes false "Checksums do not match" errors on systems where shasum
is a symlink to sha256sum or otherwise.

psychoss/nvm,williamboman/nvm,Salahudeen/nvm,DigitallySeamless/nvm,dfackler/nvm,misterdjules/nvm,PeterDaveHello/nvm,WY08271/nvm,JasonChrYoung/nvm,mmorejon/nvm,bbuck/nvm,mirydz/nvm,vinaykaradia/clone-nvm,wahyutaufik/nvm,fnogatz/swivm,Richardphp/nvm,reybango/nvm,jhliberty/nvm,LeeLovCY/nvm,bevacqua/nvm,Theodeus/nvm,Salahudeen/nvm,reybango/nvm,greyhwndz/nvm,SampleLiao/nvm,hanhailong/nvm,PeterDaveHelloKitchen/nvm,Kuzirashi/nvm,modulexcite/nvm,kmctown/nvm,Richardphp/nvm,kumaria/nvm,jaawerth/nvm,jbergstroem/nvm,elrasguno/nvm,youleiy/nvm,tlevine/nvm,creationix/nvm,evocateur/nvm,cirosantilli/nvm,tianzhihen/nvm,ljharb/nvm,NicCollins/nvm,wahyutaufik/nvm,chinazhaghai/nvm,JanChw/nvm,elrasguno/nvm,ljharb/nvm,jaawerth/nvm,domenicosolazzo/nvm,woss/nvm,evocateur/nvm,PeterDaveHelloKitchen/nvm,michael-ni/nvm,egilkh/nvm,edwmurph/nvm,IonicaBizauKitchen/nvm,williamboman/nvm,bevacqua/nvm,diegofcb10/nvm,devedbox/nvm,owen-it/nvm,kumaria/nvm,christophercaburog/nvm,tlevine/nvm,icyflame/nvm,DigitallySeamless/nvm,WY08271/nvm,JasonChrYoung/nvm,parasaro92/nvm,jhliberty/nvm,joneit/nvm,lukechilds/nvm,wskplho/nvm,hkdobrev/nvm,jbergstroem/nvm,diegofcb10/nvm,edwmurph/nvm,Kuzirashi/nvm,parasaro92/nvm,hkdobrev/nvm,mirydz/nvm,cjac/nvm,lukechilds/nvm,Theodeus/nvm,owen-it/nvm,CristianCantoro/nvm,vinaykaradia/clone-nvm,youleiy/nvm,cjac/nvm,woss/nvm,joneit/nvm,icyflame/nvm,PeterDaveHello/nvm,Ingelheim/nvm,gtdeng/nvm,slariviere/nvm,CristianCantoro/nvm,dfackler/nvm,IonicaBizauKitchen/nvm,scq000/nvm,cnpm/nvm,nontage24/nvm,cnpm/nvm,egilkh/nvm,devedbox/nvm,kmctown/nvm,SampleLiao/nvm,JanChw/nvm,sjfkai/nvm,domenicosolazzo/nvm,pmq20/nvm,cirosantilli/nvm,LeeLovCY/nvm,gtdeng/nvm,pmq20/nvm,misterdjules/nvm,creationix/nvm,modulexcite/nvm,slariviere/nvm,bbuck/nvm,christophercaburog/nvm,Ingelheim/nvm,mmorejon/nvm,thomasf/nvm,tianzhihen/nvm,hanhailong/nvm,chinazhaghai/nvm,scq000/nvm,psychoss/nvm,michael-ni/nvm,nontage24/nvm,wskplho/nvm,greyhwndz/nvm,thomasf/nvm