Remove fixed width from embedded tweets in WordPress for responsiveness

gistfile1.php

/**
 * Remove fixed width from embedded tweets. First step to make them responsive.
 * @param string $html HTML that should be used to embed
 * @param string $url The URL to the content that should be attempted to be embedded.
 * @param array $args Optional arguments.
 * @author Elio Rivero
 * @link http://www.ilovecolors.com.ar/
 */
function themesrobot_oembed_result($html, $url, $args){
    // Check if it's a tweet looking for 'twitter' in the url pasted in the post
    if( stripos($url, 'twitter') ) {
        // Before the tweet is processed, it's displayed as a blockquote
        // with its width attribute set, so let's remove it.
        return str_replace('width="500"', '', $html);
    }
    // Otherwise return the HTML as is.
    return $html;
}
// Filter the result of the oEmbed extraction.
add_filter('oembed_result', 'themesrobot_oembed_result', 10, 3);