Use a tighter `grep` to avoid `dnvm.sh` conflicts.
Use a tighter `grep` to avoid `dnvm.sh` conflicts.

Fixes #838.
thomasf/nvm,Richardphp/nvm,youleiy/nvm,fnogatz/swivm,icyflame/nvm,PeterDaveHello/nvm,mirydz/nvm,youleiy/nvm,evocateur/nvm,slariviere/nvm,Kuzirashi/nvm,Theodeus/nvm,creationix/nvm,slariviere/nvm,Ingelheim/nvm,kumaria/nvm,PeterDaveHelloKitchen/nvm,tianzhihen/nvm,dfackler/nvm,bevacqua/nvm,jhliberty/nvm,Richardphp/nvm,tlevine/nvm,lukechilds/nvm,Ingelheim/nvm,ljharb/nvm,tlevine/nvm,edwmurph/nvm,icyflame/nvm,PeterDaveHello/nvm,jaawerth/nvm,creationix/nvm,Theodeus/nvm,jaawerth/nvm,Kuzirashi/nvm,thomasf/nvm,PeterDaveHelloKitchen/nvm,kumaria/nvm,ljharb/nvm,mirydz/nvm,tianzhihen/nvm,dfackler/nvm,lukechilds/nvm,jhliberty/nvm,evocateur/nvm,bevacqua/nvm,edwmurph/nvm