Fixed Node installer to detect Node and version

Ensures the latest version of Node is installed as managed by Fast
Node Manager (FNM). Behavior is similar to using Frum to manage Ruby
versions except FNM has the additional feature of computing latest
version instead.

lib/installers.sh

@@ -201,8 +201,8 @@ export -f install_program
 # Installs Node.
 # Parameters: None.
 install_node() {
-  if ! command -v fnm > /dev/null; then
-    $(get_homebrew_bin_root)/fnm install --lts
+  if [[ ! -x "$(command -v node)" ]]; then
+    "$(get_homebrew_bin_root)/fnm" install --latest
   fi
 }
 export -f install_node