[Bug] Missing og:image on non episode pages

[rajeshduggal]

Expected behavior

Theme should allow config of a default og:image to be present on non-episode pages. e.g. the home page. So that a particular configured image is pulled into a facebook posts the link is shared in facebook.

Actual behavior

When a facebook user shares the homepage link in a facebook post, it might pull an arbitrary image into the posting.

Reproduction Steps

Post the website homepage in facebook and notice the image pulled. Also view source on the home page and notice missing og:image tag.

[mattstratton]

Connected to #172