title: BrowserSync with custom URL
body: <p>Im using BrowserSync for my site. The following live reloads my CSS changes but it opens a webpage at <a href="http://localhost:3000/" rel="noreferrer">http://localhost:3000/</a></p>
  
  <pre><code>gulp.task('sass-watch', ['theme-css'], browserSync.reload);
  
  gulp.task('browser-sync', function() {
    var files = [
      'htdocs/themes/custom/my-theme/dist/*'
    ];
    browserSync.init(files,{
      proxy: 'mysite.com'
    });
  });
  </code></pre>
  
  <p>My site is configured via Vagrant to be accessed locally at mysite.com. How can I get BrowserSync working at this custom URL? </p>
  
  <p>Ive tried the following as my VM is using port 80. </p>
  
  <pre><code>gulp.task('browser-sync', function() {
    var files = [
      'htdocs/themes/custom/my-theme/dist/*'
    ];
    browserSync.init(files,{
      open: 'external',
      host: 'mysite.com',
      proxy: 'mysite.com',
      port: 80
    });
  });
  </code></pre>
  
  <p>However I get an error:</p>
  
  <pre><code>events.js:141
        throw er; // Unhandled 'error' event
        ^
  
  Error: listen EACCES 0.0.0.0:80
      at Object.exports._errnoException (util.js:874:11)
      at exports._exceptionWithHostPort (util.js:897:20)
      at Server._listen2 (net.js:1221:19)
      at listen (net.js:1270:10)
      at Server.listen (net.js:1366:5)
      at module.exports.plugin (/path-to-my-site/node_modules/browser-sync/lib/server/index.js:24:25)
      at Object.module.exports.startServer [as fn] (/path-to-my-site/node_modules/browser-sync/lib/async.js:236:52)
      at /path-to-my-site/node_modules/browser-sync/lib/browser-sync.js:149:14
      at iterate (/path-to-my-site/node_modules/browser-sync/node_modules/async-each-series/index.js:8:5)
      at /path-to-my-site/node_modules/browser-sync/node_modules/async-each-series/index.js:16:16
  </code></pre>
  
  <p>If I use the default port of 3000 then the page loads but I get error connection refused. </p>
  
  <p>ERR_CONNECTION_REFUSED</p>