OverloadedStrings is an extension that basically puts `fromString` in front of every string literal. This means that instead of having type `String`, string li

OverloadedStrings is an extension that basically puts `fromString` in front of every string literal. This means that instead of having type `String`, string literals have type `IsString a => a` (meaning "for anything that implements `IsString`, this could be a that"). It's used here so that `"http:"` can be used as a `ByteString` without cluttering the code up with an explicit `fromString`.