Added hint for node version min requirement

jsdoc does not seem to work with node 5 or below

- updated README
- added .nvmrc
- added engine section to package.json

Author: Zehua Liu

.nvmrc

@@ -0,0 +1 @@
+6

README.md

@@ -36,6 +36,14 @@ For more details on configuring the server, see [http-server docs][http-server].
 
 ## Development
 
+### Node version
+
+Node 6 or above is required in order to build jsdoc.
+
+If you are using [nvm](https://github.com/creationix/nvm#nvmrc), simply run:
+
+	nvm install && nvm use
+
 ### Building docs
 
 To rebuild the [docs](./docs/index.html) page:

package.json

@@ -2,6 +2,7 @@
   "name": "ramda.github.io",
   "version": "0.24.1",
   "description": "Ramda website",
+  "engines" : { "node" : ">=6.0.0" },
   "private": true,
   "repository": {
     "type": "git",