Allow users to opt into tracks and show them the correct content for their track

[mattstauffer]

• New to coding
• Frontend programmer
• WordPress programmer

[mattstauffer]

We've built the tracks, but A) they're not fleshed out in the live content or the seeders and B) users can't opt in to which track they're using yet, so this isn't quite done yet.

[jonsugar]

@mattstauffer I think this can be closed due to #24

[mattstauffer]

I think we can just say that whatever closes #24 will also at least partially close this--but I want to make sure we consider actually applying the chosen track, which may not get done in the PR that closes #24. Thanks!

[tammytee]

This looks like a duplicate of #166 ? If so, PR #169 resolves this.