Bugfix/microdata content value

Value nodes with a [content] attribute will now pull from that attribute... rather than the value of text(). For example:

    <div>
        <h1 itemprop="name">Mexican Rigatoni and Cheese</h1>
    </div>

    <div>
        <span>Prep:</span>
        <span itemprop="prepTime" content="PT30M">30 mins</span>
    </div>

The value for the [_name_] property will continue to be "_Mexican Rigatoni and Cheese_". The value for the [_prepTime_] attribute will be "_PT30M_" instead of "_30 mins_".