Specify node 6 requirement

CONTRIBUTING.md

@@ -25,13 +25,13 @@ All source code is written in [TypeScript](http://www.typescriptlang.org/Handboo
 
 ### Installing Node.js and npm
 
-Building the JupyterLab from its GitHub source code requires Node.js and 
-Node's package manager, ``npm``.
+Building the JupyterLab from its GitHub source code requires Node.js version 
+6+ and Node's package manager, ``npm``.
 
 If you use ``conda``, you can get them with:
 
 ```bash
-conda install -c javascript nodejs
+conda install -c conda-forge nodejs
 ```
 
 If you use [Homebrew](http://brew.sh/) on Mac OS X:
@@ -40,14 +40,6 @@ If you use [Homebrew](http://brew.sh/) on Mac OS X:
 brew install node
 ```
 
-For Debian/Ubuntu systems, you should use the ``nodejs-legacy`` package instead
-of the ``node`` package:
-
-```bash
-sudo apt-get update
-sudo apt-get install nodejs-legacy npm
-```
-
 You can also use the installer from the [Node.js](https://nodejs.org) website.
 
 

docs/extensions_user.md

@@ -6,12 +6,12 @@ output renderers for example.
 
 ### Installing Node.js and npm
 
-Installing JupyterLab extensions requires Node.js and Node's package manager, ``npm``.
+Installing JupyterLab extensions requires Node.js version 6+ and Node's package manager, ``npm``.
 
 If you use ``conda``, you can get them with:
 
 ```bash
-conda install -c javascript nodejs
+conda install -c conda-force nodejs
 ```
 
 If you use [Homebrew](http://brew.sh/) on Mac OS X:
@@ -20,14 +20,6 @@ If you use [Homebrew](http://brew.sh/) on Mac OS X:
 brew install node
 ```
 
-For Debian/Ubuntu systems, you should use the ``nodejs-legacy`` package instead
-of the ``node`` package:
-
-```bash
-sudo apt-get update
-sudo apt-get install nodejs-legacy npm
-```
-
 ### Installing Extensions
 
 The base JupyterLab application comes with core set of extensions, which