Replacing debug prints with proper logging, main scrape.py cleanup

This pull request includes two major "cleanup" related changes:
 - It replaces the print() calls in different places in the scraping code with Python logging calls. This allows for much better control over what gets printed out and how (fixes niryariv/opentaba-server#46)
 - It cleans up the scrape.py script to a more recommended main function + `if __name__ == '__main__'` style construct in the global scope. This allows for some reusability of the main scraping function, for example in testing or other forms of automation, and is generally considered cleaner. 

Feel free to merge or not, this is a "suggestion" pull request :)