Use HTTPS for ES API requests

[seeeeew]

Since the ES API server seems to support HTTPS for all requests, this shouldn't change anything for most users, but it would greatly reduce conflicts with HTTPS Everywhere. I've tested this in Chrome for almost two weeks with HTTPS Everywhere disabled to ensure it won't cause any problems for regular users.

Although some rare problems might persist for HTTPS Everywhere users, I consider the three issues mentioned in my commit message (#1319, #1432, #1445) fixed, because this is probably the best we can get without Steam allowing HTTPS for all API requests (or us proxying them).

I'm not convinced the conflicts with HTTPS Everywhere are our fault, but if we can easily fix (or at least improve) them, we should do so.

[DFNCTSC]

@jshackles Please merge this fix into master ASAP. Thanks! <3

@seeeeew

I'm not convinced the conflicts with HTTPS Everywhere are our fault

It's technically steampowered.com's fault due to it's content policies, but since we're trying to change how the site works by default the blame can be put on whomever you want. 😝 Thanks for the fix commit!

[jshackles]

I've been testing this branch and it does indeed seem to work and resolve these issues for the most part. It's definitely on Valve to get their shit together when it comes to HTTPS requests on Steam, but at least we can attempt to fix interoperability with another major addon in the mean time.