Added command nvm install stable

nvm auto-detects last stable relase and fetch it.

nvm.sh

@@ -54,7 +54,11 @@ nvm_version() {
 
 nvm_remote_version() {
     local PATTERN=$1
+    if [[ $PATTERN == "stable" ]]; then
+      VERSION=`nvm_last_stable_version`
+    else
       VERSION=`nvm_ls_remote $PATTERN | tail -n1`
+    fi
     echo "$VERSION"
 
     if [ "$VERSION" = 'N/A' ]; then
@@ -111,6 +115,17 @@ nvm_ls_remote() {
     return
 }
 
+nvm_last_stable_version(){
+  local VERSION
+  VERSION=`curl http://nodejs.org/dist/latest/ | grep -o 'node-v.*\"' -m 1 | grep -o 'v[0-9]*\.[0-9]*\.[0-9]*'`
+  if [ ! "$VERSION" ]; then
+    echo "N/A"
+    return
+  fi
+  echo "$VERSION"
+  return
+}
+
 nvm_checksum() {
     if [ "$1" = "$2" ]; then
         return