[BUGFIX] fix compatibility issues when switching node version

This is a temporary fix related to https://github.com/creationix/nvm/issues/855.

core/cli.sh

@@ -41,7 +41,7 @@ else
 	if [ ! $OSTYPE == "msys" ]
 	then
 		# set node version
-		nvm use ${nodeversion}
+		nvm use --delete-prefix ${nodeversion}
 	else
 		# interestingly, setting the node version here will break on windows. for some reason the node and npm commands
 		# wont't be available anymore afterwards. tell the user instead.

install.sh

@@ -49,7 +49,7 @@ nvm install ${nodeversion}
 # nvm-windows won't set the version by default after installing it
 if [ $OSTYPE == "msys" ]
 then
-	nvm use ${nodeversion}
+	nvm use --delete-prefix ${nodeversion}
 fi
 
 echo -e "\033[0;32mNode installed ✓\033[0m\n"