Fix Google Lighthouse errors

[jbampton]

I will be working on some of the list of issues from the current master from the Lighthouse report attached.

I have already started with PR #84

Google Lighthouse is an open-source, automated tool for measuring the quality of web pages. It can be run against any web page, public or requiring authentication. Google Lighthouse audits performance, accessibility and search engine optimization of web pages.

https://developers.google.com/web/tools/lighthouse

mruby-site-lighthouse.pdf