Fix small issue with Twitter meta

Author: gnclmorais

app/views/shared/_meta_tags.html.haml

@@ -6,4 +6,4 @@
 %meta{ property: 'og:site_name', content: 'codebar' }
 %meta{ property: 'og:locale', content: 'en_GB' }
 -# Only Twitter-specific tag needed
-%meta{ name: 'twitter:card', content: image_url('logo-square.png') }
+%meta{ name: 'twitter:card', content: 'summary_large_image' }