Prevent memory leaks using Selenium

If you're having zombie chrome processes using selenium, it could be due to failing to quit selenium when uncaught exceptions occur.

Use python "context manager" to ensure selenium quits/exits properly

with Scraper() as s:
    s.fetch()

class Scraper:
    def __init__(self):
        self.driver = get_chromedriver()

    def fetch(self):
        pass

    def __enter__(self):
        return self

    def __exit__(self, *exc):
        if self.driver:
            self.driver.quit()