title: webdriverio throws element not visible error after settings its value
body: <p>Trying nodejs and webdriverio first time. This seems to be pretty simple stuff when tried in watir-webdriver or selenium-webdriver gems,but this is confusing me in webdriverio. Why I am getting this error when the driver is already finding the element and setting the value</p>
  
  <pre><code>var webdriverio = require('webdriverio');
  var options = {
  desiredCapabilities: {
  browserName: 'firefox'
  }
  };
  var client=webdriverio.remote(options);
  
  client
  .init()
  .url('http://www.twitter.com').title(function(err, res) {
  console.log('Title was: ' + res.value);
  })
  .isExisting('#signin-password')
  .then(function(isExisting){
      console.log(isExisting);
  })
  .setValue('#signin-password','password')
  .then(function(){
      console.log("password set");
  })
  .isExisting('#signin-email')
  .then(function(isExisting){
      console.log("email"+isExisting);
  })
  .setValue('#signin-email','username')
  .then(function(){
      console.log("username set");
  });
  </code></pre>
  
  <p>The error I am getting is</p>
  
  <pre><code>Title was: Welcome to Twitter - Login or Sign up
  true
  RuntimeError: Element is not currently visible and so may not be interacted with
  Build info: version: '2.47.1', revision: '411b314', time: '2015-07-30 03:03:16'
  System info: host: 'DTNBNAUD10806XS', ip: '10.36.179.144', os.name: 'Windows 7', os.arch: 'amd64', os.version: '6.1', java.version: '1.8.0_05'
  Driver info: driver.version: unknown
      at elementIdValue("1", "password") -     at C:\Development\node_modules\webdriverio\lib\commands\setValue.js:52:7
  </code></pre>