Run node and io.js installation test suites separately.

test/installation_node/install already installed uses it

@@ -0,0 +1,24 @@
+#!/bin/sh
+
+die () { echo $@ ; exit 1; }
+
+. ../../nvm.sh
+
+[ "$(nvm install invalid.invalid 2>&1)" = "Version 'invalid.invalid' not found - try \`nvm ls-remote\` to browse available versions." ] || die "nvm installing an invalid version did not print a nice error message"
+
+# Remove the stuff we're clobbering.
+[ -e ../../v0.9.7 ] && rm -R ../../v0.9.7
+[ -e ../../v0.9.12 ] && rm -R ../../v0.9.12
+
+# Install from binary
+nvm install 0.9.7
+nvm install 0.9.12
+
+nvm use 0.9.7
+
+node --version | grep v0.9.7 || die "precondition failed: node doesn't start at 0.9.7"
+
+nvm install 0.9.12
+
+node --version | grep v0.9.12 || die "nvm install on already installed version doesn't use it"
+