Add retries to crawler

[eleweek]

In the episode 6 (http://www.youtube.com/watch?v=dAp0GkWSxaA) I noticed that crawler crashes when it tries to get current_page (current_page = downloadRedditUrl(current_page_url)). It would be nice to have retries here.

[CheoR]

this gives a simple workaround for the 504 HTTP Error 504 Gateway timeout , from the link, "This problem is entirely due to slow IP communication between back-end computers, possibly including the Web server. Only the people who set up the network at the site which hosts the Web server can fix this problem."

[eleweek]

Hm, this issue may still be relevant in certain parts. The project uses reddit api/praw now though