title: Yargs documenting a flag
body: <p>I was trying to figure out how to document and alias a param that takes no values with <a href="https://github.com/bcoe/yargs" rel="nofollow"><code>yargs</code></a></p>
  
  <p>What I want to do is alias <code>-c</code> to <code>--compile</code> and be able to document <code>--compile</code>. If <code>--compile</code></p>
  
  <p><code>script sources -c</code></p>
  
  <p>I was expecting it to be something like this</p>
  
  <pre><code>  var argv = require('yargs')
      .usage('Usage: $0 &lt;input&gt; [options]')
      .example('$0 src/**.js -c', 'Generate a build')
      .demand(1)
  
      .boolean('compile')
      .alias('compile', ['c'])
      .nargs('c', 1)
      .describe('compile', 'Whether to compile the results')
  
      .version(function() {
        return require('../package').version;
      })
      .argv;
  </code></pre>
  
  <p>However, calling <code>script sources -c</code> will generate an error</p>
  
  <pre><code>TypeError: Cannot read property 'newAliases' of undefined
      at Object.self.help (/home/gyeates/code/lodash.modularize/node_modules/yargs/lib/usage.js:135:45)
      at Object.self.showHelp (/home/gyeates/code/lodash.modularize/node_modules/yargs/lib/usage.js:211:29)
      at Object.Argv.self.showHelp (/home/gyeates/code/lodash.modularize/node_modules/yargs/index.js:303:15)
      at Object.self.fail (/home/gyeates/code/lodash.modularize/node_modules/yargs/lib/usage.js:37:39)
  </code></pre>