Improve page titles for SEO

[croaky]

Google rewrites page titles in search results:

https://support.google.com/webmasters/answer/35624?hl=en

See the Trello card for screenshots of podcasts.thoughtbot.com page titles
being re-written in Google search results:

https://trello.com/c/3rO5yDi2

Since we can rely on Google adding "thoughtbot" and "podcast" to the page
title for search queries, this commit simplifies our page title strategy:

• Home page: "thoughtbot podcasts"
• Podcast page: "Giant Robots Smashing Into Other Giant Robots Podcast"
• Episode page: "CoreFrustration (Reda Lemeden)"

Since we don't need Flutie's page_title method, and weren't using its
other method, body_class, it can be removed.

This commit also fixes a yield(:meta_description) || problem by using
yield(:meta_description).presence ||. yield without a content_for
returns an empty string, no nil.

All page title and meta description specs have been consolidated in the
spec/features/google_results_spec.rb file.

[cpytel]

The code looks fine and ready to merge.

I've read through the docs, but I'm not sure I understand where our name comes from (I guess Thoughtbot Podcast in this case)

[croaky]

The code looks fine and ready to merge.

Thanks.

I've read through the docs, but I'm not sure I understand where our name comes from (I guess Thoughtbot Podcast in this case)

You mean on the SERP? Google is automatically adding it. It's looking at the keywords in the search and noticing that we have "podcasts" and "thoughtbot" in our domain name (and probably in the markup), so its algorithm thinks a better title to show in that particular search is to add those keywords.