Add nvm_iojs_prefix

test/fast/Unit tests/nvm_iojs_prefix

@@ -0,0 +1,7 @@
+#!/bin/sh
+
+die () { echo $@ ; exit 1; }
+
+. ../../../nvm.sh
+
+[ "$(nvm_iojs_prefix)" = "iojs" ] || die '"nvm_iojs_prefix" did not return the string "iojs". why did this fail?!'