Set default metatags

[spencerldixon]

We can probably set a bunch of defaults that are helpful in rendering opengraph tags. We can use a placeholder image to the opengraph image. We'll need to set some things like app name and description in en.yml

<%= tag :meta, property: 'og:title', content: t('app.name') %>
<%= tag :meta, property: 'og:description', content: t('app.description') %>
<%= tag :meta, property: 'og:type', content: "website" %>
<%= tag :meta, property: 'og:image', content: asset_path('ogimage.png') %>
<%= tag :meta, property: 'og:url', content: request.original_url %>