Changed API URL to match the new one, and added delete function
New arguments (as they're reworked now):
-t <token> - With this argument, you specify your files.co.pl token.
-u - Tells the client that you want to upload the file from your computer.
-d - Tells the client that you want to delete the file that is already uploaded
-f <filename> - With that argument, you specify the file that you want to upload/delete.