Share button scripts with `async`. See http://myakura.hatenablog.com/entry/2014/10/14/061713

_shareButtons.html

<div data-href="http://YOUR-URL-GOES-HERE" data-layout="button_count" class="fb-share-button"></div>
<script src="//connect.facebook.net/en_US/sdk.js#xfbml=1&amp;version=v2.0" id="facebook-jssdk" async></script>

<a href="https://twitter.com/share" class="twitter-share-button">Tweet</a>
<script src="//platform.twitter.com/widgets.js" id="twitter-wjs" async></script>

<div data-size="medium" class="g-plusone"></div>
<script src="https://apis.google.com/js/platform.js" async defer></script>

<a href="http://b.hatena.ne.jp/entry/" data-hatena-bookmark-layout="standard-balloon" data-hatena-bookmark-lang="en" class="hatena-bookmark-button"></a>
<script src="http://b.st-hatena.com/js/bookmark_button.js" async></script>

_shareButtons.jade

//- Facebook
//- https://developers.facebook.com/docs/plugins/share-button/
div.fb-share-button( data-href = "http://YOUR-URL-GOES-HERE", data-layout = "button_count" )
script( src = "//connect.facebook.net/en_US/sdk.js#xfbml=1&version=v2.0", id = "facebook-jssdk", async )

//- Twitter
//- https://dev.twitter.com/web/tweet-button
a.twitter-share-button( href = "https://twitter.com/share" ) Tweet
script( src = "//platform.twitter.com/widgets.js", id = "twitter-wjs", async )

//- Google+
//- https://developers.google.com/+/web/+1button/
div.g-plusone( data-size = "medium" )
script( src = "https://apis.google.com/js/platform.js", async, defer )

//- Hatena Bookmark
//- http://b.hatena.ne.jp/guide/bbutton
a.hatena-bookmark-button( href = "http://b.hatena.ne.jp/entry/", data-hatena-bookmark-layout = "standard-balloon", data-hatena-bookmark-lang = "en" )
script( src = "http://b.st-hatena.com/js/bookmark_button.js", async )