Add argparse to make it more pythonic

[managedkaos]

Get help:

22:05 $ ./hackernews.py -h
usage: hackernews.py [-h] [int]

positional arguments:
  int         Then number of news items to return, from 1 to 30

optional arguments:
  -h, --help  show this help message and exit

Default is 10:

22:08 $ ./hackernews.py
1. Video Games Are Destroying the People Who Make Them
https://www.nytimes.com/2017/10/25/opinion/work-culture-video-games-crunch.html

2. Microsoft Has Stopped Manufacturing The Kinect
https://www.fastcodesign.com/90147868/exclusive-microsoft-has-stopped-manufacturing-the-kinect
...

Get more than 10:

22:08 $ ./hackernews.py 20

But you can only get 30:

22:08 $ ./hackernews.py 31
usage: hackernews.py [-h] [int]
hackernews.py: error: argument int: invalid choice: 31 (choose from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)