Fix broken escape sequences on FAQ and install pages

[Pokechu22]

For the most part, text surrounded by backticks is automatically escaped, so the backslashes or HTML escapes were showing up on the page, which is confusing. For the FAQ page, I've removed the backslashes. For the install page, I've used the <var> element which is more semantically correct (and results in italic formatting); that's not directly exposed in markdown, so I had to use code tags instead of backticks.

I haven't tested this beyond confirming that the pages now appear correctly on GitHub.

Here's what the pages looked like before this fix:

[ISSOtm]

Thanks! I think the escapes for the angle brackets are holdovers from the Jekyll days.

[Pokechu22]

Hmm, it seems like <code> gets styled a bit differently from backticks:

It looks like it's getting treated as <pre><code>. But, eh, I think this is readable enough and it's definitely an improvement over what was there before.