Add `nvm_is_merged_node_version`

nvm.sh

@@ -927,6 +927,10 @@ nvm_ensure_default_set() {
   return $EXIT_CODE
 }
 
+nvm_is_merged_node_version() {
+   nvm_version_greater_than_or_equal_to "$1" v4.0.0
+}
+
 nvm_install_iojs_binary() {
   local NVM_IOJS_TYPE
   NVM_IOJS_TYPE="$1"

test/fast/Unit tests/nvm_is_merged_node_version

@@ -0,0 +1,10 @@
+#!/bin/sh
+
+die () { echo $@ ; exit 1; }
+
+. ../../../nvm.sh
+
+nvm_is_merged_node_version '4.0' || die '"nvm_is_merged_node_version 4.0 was not true'
+nvm_is_merged_node_version '5.1' || die '"nvm_is_merged_node_version 5.1 was not true'
+! nvm_is_merged_node_version '3.99' || die '"nvm_is_merged_node_version 3.99 was not false'
+! nvm_is_merged_node_version 'v1.0.0' || die '"nvm_is_merged_node_version v1.0.0" was not false'