opengraph meta properties

I was using your plugin and would like to propose and update or a minor fix.

In the social_sharing_toolkit.php version 2.1.1 line 515 I believe that the og:description should be escaped.

<meta property="og:description" content="'.esc_attr($excerpt).'"/>';

Because if the user puts in the excerpt double quotes, it breaks the meta tag and shows “/> on the top of the page.

It might apply to other meta tags. Didn’t check 🙂

Thanks!

http://ww.wp.xz.cn/extend/plugins/social-sharing-toolkit/