Add info on a few gotchas.

Author: aparajita

README.md

@@ -9,13 +9,15 @@ SublimeLinter 3 must be installed in order to use this plugin. If SublimeLinter
 ### Linter installation
 Before installing this plugin, you must ensure that `csslint` is installed on your system. To install `csslint`, do the following:
 
-1. Install [Node.js](http://nodejs.org).
+1. Install [Node.js](http://nodejs.org) (and [npm](https://github.com/joyent/node/wiki/Installing-Node.js-via-package-manager) on Linux).
 
 1. Install `csslint` by typing the following in a terminal:
    ```
    npm install -g csslint
    ```
 
+1. If you are using `nvm` and `zsh`, ensure that the line to load `nvm` is in `.zprofile` and not `.zshrc`.
+
 Once csslint is installed, you can proceed to install the SublimeLinter-csslint plugin if it is not yet installed.
 
 ### Plugin installation