change accountSwitcher.js to always use HTTPS

Move all accountSwitcher login requests to HTTPS and stop using `ssl.reddit.com`.

(fixes account switcher for Chrome incognito)

Formerly `accountSwitcher.js` used an unsecured request to `www.reddit.com` to log in when in Chrome incognito mode, as `ssl.reddit.com` cookies were not allowed. Now that reddit supports HTTPS site-wide, that call is blocked by Chrome (as it should be) and unnecessary, as plain `reddit.com` can be accessed via HTTPS.

See https://www.reddit.com/r/RESissues/comments/2gcsi1/bug_account_switcher_loads_nonhttps_api_login/



This commit changes how logins work for everybody on all browsers, so um... test it carefully.
Ditto.