Add support for OSRS

[mswdev]

Add support for OSRS possibly?

@michaelbull If this is something you don't have time for, I'd be willing to add support for it and make a pull request.

[michaelbull]

Do these not work?

[mswdev]

Do these not work?

I didn't realize that OSRS was supported in terms of hiscores as the readme and project information only mentions RuneScape generically rather than RuneScape 3 and or OSRS.

What about OSRS G.E data, If I'm not mistaken, that doesn't look to be supported?

[michaelbull]

Yeah doesn't look like the OSRS GE is supported, however there is documentation for it here.

I think it would be a case of tackling this hardcoded URL, making it an enum along the lines of the HiscoresTable, passing it to the functions inside of the GrandExchange class - in a similar fashion to the methods inside Hiscores.