title: npm install -g less does not work: EACCES: permission denied
body: <p>I'm trying to set up less on phpstorm so I can compile .less files to .css on save. I have installed node.js and the next step (according to this <a href="https://www.jetbrains.com/webstorm/help/transpiling-sass-less-and-scss-to-css.html" rel="noreferrer">https://www.jetbrains.com/webstorm/help/transpiling-sass-less-and-scss-to-css.html</a>) is running this command in the terminal </p>
  
  <pre><code>npm install -g less
  </code></pre>
  
  <p>However when I do this I get these errors</p>
  
  <pre><code>☁  ~  npm install -g less
  npm WARN install Couldn't install optional dependency: EACCES: permission denied, mkdir '/Users/brentscholl/.npm/mkdirp/0.5.1'
  npm WARN install Couldn't install optional dependency: EACCES: permission denied, mkdir '/Users/brentscholl/.npm/graceful-fs/3.0.8'
  npm WARN install Couldn't install optional dependency: EACCES: permission denied, mkdir '/Users/brentscholl/.npm/extend/3.0.0'
  npm WARN install Couldn't install optional dependency: EACCES: permission denied, mkdir '/Users/brentscholl/.npm/readable-stream/2.0.4'
  npm WARN install Couldn't install optional dependency: EACCES: permission denied, mkdir '/Users/brentscholl/.npm/chalk/1.1.1'
  npm WARN install Couldn't install optional dependency: EACCES: permission denied, mkdir '/Users/brentscholl/.npm/xtend/4.0.1'
  npm WARN checkPermissions Missing write access to /usr/local/lib/node_modules
  /usr/local/lib
  └─┬ less@2.5.3
    ├─┬ errno@0.1.4
    │ └── prr@0.0.0
    ├── image-size@0.3.5
    ├── mime@1.3.4
    ├─┬ promise@6.1.0
    │ └── asap@1.0.0
    └─┬ source-map@0.4.4
      └── amdefine@1.0.0
  
  npm ERR! Darwin 15.0.0
  npm ERR! argv "/usr/local/bin/node" "/usr/local/bin/npm" "install" "-g" "less"
  npm ERR! node v5.0.0
  npm ERR! npm  v3.3.6
  npm ERR! path /usr/local/lib/node_modules
  npm ERR! code EACCES
  npm ERR! errno -13
  npm ERR! syscall access
  
  npm ERR! Error: EACCES: permission denied, access '/usr/local/lib/node_modules'
  npm ERR!     at Error (native)
  npm ERR!  { [Error: EACCES: permission denied, access '/usr/local/lib/node_modules']
  npm ERR!   errno: -13,
  npm ERR!   code: 'EACCES',
  npm ERR!   syscall: 'access',
  npm ERR!   path: '/usr/local/lib/node_modules' }
  npm ERR!
  npm ERR! Please try running this command again as root/Administrator.
  
  npm ERR! Please include the following file with any support request:
  npm ERR!     /Users/brentscholl/npm-debug.log
  </code></pre>
  
  <p>I'm a complete noob here and not sure what to do next. Any help would be very appreciated!</p>