Support for creationix/nvm

Adds support for nvm inside the node module.

If `.nvm/nvm.sh` is found, it is sourced, similar to the way rvm,
rbenv and others work.

modules/node/init.zsh

@@ -5,6 +5,11 @@
 #   Sorin Ionescu <sorin.ionescu@gmail.com>
 #
 
+# Load NVM into the shell session.
+if [[ -s "$HOME/.nvm/nvm.sh" ]]; then
+  source "$HOME/.nvm/nvm.sh"
+fi
+
 # Return if requirements are not found.
 if (( ! $+commands[node] )); then
   return 1