Keyboard

PR for #80

This is a test I was using:

``` php
<?php
// before: "VALUE"

        $el->sendKeys(array(WebDriverKeys::CONTROL,'a'),'test');
        $webdriver->getKeyboard()
            ->press(WebDriverKeys::SHIFT)
            ->sendKeys('111')
            ->release(WebDriverKeys::SHIFT)
            ->sendKeys('1');

// after: "test!!!1"
?>
```

One question: what about comments in docblocks? Should they be in interfaces or in remote classes? Basically they are duplicating. So probably remote classes should use {inheritdoc} notation.