Check whether Node is installed; update README to include Node installation link

README.rst

@@ -18,6 +18,8 @@ Installation
 The intent of this project is to be installed as Django apps that will be
 included in `edx-platform <https://github.com/edx/edx-platform>`_.
 
+For JavaScript minification and unit tests, you must `install NodeJS <http://nodejs.org/>`_.
+
 To install dependencies and start the development ("workbench") server:
 
 .. code:: bash

scripts/install.sh

@@ -16,6 +16,11 @@ echo "Installing XBlock..."
 pip install -q -e .
 
 echo "Installing Node requirements..."
+if [ -z `which npm` ]; then
+    echo "Please install NodeJS: http://nodejs.org/"
+    exit 1
+fi
+
 npm config set loglevel warn
 npm install