get_beer_data.php can return json files in wrong order

[mikefelix]

I run BrewPi on my Ubuntu server instead of a RPi. I ran into an issue with my graph data not displaying correctly once midnight came and went. I discovered that this file is using readdir(), which is specified in the PHP docs to return files in the order they are stored in the filesystem (i.e. what you get if you run ls -U). For whatever reason, ls -U returns the files in reverse order on my system (test-2014-08-29.json comes before test-2014-08-28.json) and this is the order readdir() is getting them, which confuses the graph. Changing the file to use scandir() instead fixed the issue for me because scandir() sorts the filenames alphabetically despite their filesystem order.