Issue title: Usage of H tags is bad for SEO
 Issue body: Currently this theme uses an H1 tag around the site name, and an H2 tag around the page title. Apart from the fact that this makes the page title look the same as all the primary headers on the page, it's also bad for SEO. Search Engines look for the page title in the H1 tag (there should only ever be one H1) and will rank a site lower if all pages appear to have the same title. 

Proposed changes:
- The site name should be wrapped in a DIV or SPAN rather than an H1.
- The page title should be wrapped in an H1 rather than an H2.

 Comments: 
 Comment 0: See #172, I think they can be combined. Of course you can't control what someone does in the page's content as h1 elements are possible. Could also control the size of the page title on the screen, h1 might be a bit large. Will have to meganblack@example.net.

 Comment 1: Yep, totally agree we can't stop them adding additional H1s. But yeah, having the autogenerated one correct would be nice 😊 

 Comment 2: I'm marking this a bug as MediaWiki.org uses the `<h1>` tag for their own page titles. We should follow SEO and good practices as best we can. This would call for some tweaks to a few things. Added to both the 1.2 and 2.0 milestones.

 Comment 3: Working on this. Will probably call for a change to the page title size. H1 is huge 😉 
 Comment 4: Fixed, but left H1 size will leave it up to user to reduce
{'source': 'GithubIssues', 'repo_name_with_owner': 'jthingelstad/foreground', 'issue_id': 45202391, 'repo_stars': 140.0}