Add Missing k and field Arguments to main_ex1

After speaking with the professor during the T1 class, it was determined that the hand-in specifications for the first exercise were incomplete. The values of 'k' and 'field' to order by were missing as command-line arguments and needed to be added to the main function.

The README.MD now correctly displays how the first exercise's executable is meant to be run.

$ ./main_ex1 <path_to_csv_file> <output_csv_file> <k> <field>