error handling zip for win

[zenyusy]

Hello,
found a few bugs in handling zip archive for windows platform:

install-node/install.sh

Lines 260 to 265 in 066fc81

	EXT=tar.gz
	if [ "${PLATFORM}" = win ]; then
	EXT=zip
	fi
	URL="${BASE_URL}/${RESOLVED}/node-${RESOLVED}-${PLATFORM}-${ARCH}.tar.gz"

EXT is set to "zip" for win, but not used in URL

install-node/install.sh

Lines 272 to 274 in 066fc81

	if [ "${EXT}" = zip ]; then
	fetch "${URL}" \
	| tar xzf${VERBOSE} - \

unzip rather than tar should be used to extract zip. (btw, it is a bit tricky for unzip to achieve tar's "strip-component")

thanks for your attention