Fix homepage url restriction

[ljluestc]

Fixes issue #134 (originally #455): href url in news html source and scrape urls from Newspaper counts differ.

Changes

• Added restrict_to_homepage_urls option to newspaper.build to limit articles to homepage <a href> links.
• Integrated BeautifulSoup for homepage URL extraction.
• Fixed indexing bug in user example code.
• Added test case for Reuters homepage scraping.
• Updated documentation with new option.

Testing

• Verified ~300 articles scraped from Reuters homepage.
• Ensured article URLs match homepage patterns.
• Tested error handling for failed downloads.
• Ran existing test suite to confirm no regressions.