Answer

<?php

  /**
   *  Shortcode look like this.
   *  [tweet url="http://www.yourwebsitename.com"] Twitter [/tweet]
  */

  add_shortcode ( "tweet" , "ease_button" );
  function ease_button( $atts, $content ) {  
    extract(shortcode_atts( array(
              "url"     => false,     
    ), $atts ));

    $url = ( $atts[\'url\'] ) ? $atts[\'url\'] : \'#\';    
    return sprintf( \'<a href="%s"> %s </a>\',$url, $content );
  }
?>