install.sh: use a more generic SOURCE_STR
install.sh: use a more generic SOURCE_STR

SOURCE_STR currently includes the value of $HOME (at install time).
Change SOURCE_STR to include a literal "$HOME" (to be expanded at
profile runtime) so that sourcing nvm will work if the user changes
their username, shares their profile, et cetera.

Also use the more portable single-square-bracket test.

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