Keeping it working + small changes.

I wanted to use this API again for another project so I brought it up to date. Here's an complete list of the changes:

* Changed getLeague from v2.3 to v2.4
* Changed getTeam from v2.2 to v2.3
* Changed API_URL's from http://prod.api.pvp.net... to http://{region}.api.pvp.net, since running it with "prod" didn't work for me.
* changed request() to not enforce rate-limiting on static calls.
* I made a const called DECODE_ENABLED. When false, it returns JSON, but when true, it returns your data as json_decode($data). Maybe it's unnecessary, but I feel this is useful...
* Riot's API added two new calls, Match and Matchhistory, so I added these as functions.