Catch KeyboardInterrupt exceptions gracefully

[falkecarlsen]

When prompting for custom input a ctrl + c will print a stacktrace from the line of the input function call.

user@thinktop ~> spotirec -gc
OAuth token is expired, refreshing...
Did not receive new refresh token, saving old
0: hip-hop                                 1: pop                                     2: disco
3: soul                                    4: indie-pop                               5: rock
6: electro                                 7: edm
Enter integer identifiers for 1-5 whitespace separated selections that you wish to include [default: top 5]:
^CTraceback (most recent call last):
  File "/usr/bin/spotirec", line 727, in <module>
    parse()
  File "/usr/bin/spotirec", line 694, in parse
    print_choices(data=get_user_top_genres(), sort=True)
  File "/usr/bin/spotirec", line 194, in print_choices
    input_string = input('Enter integer identifiers for 1-5 whitespace separated selections that you wish to '
KeyboardInterrupt

Catching this exception and simply exiting with a non-zero should suffice.