Fix EZTV tracker to use the RSS feeds at our disposal

[tchoutri]

Here is an overview of the changes:

• We are now using the RSS endpoint
• Parsing is still done with Floki (The best at parsing XML and providing a simple and efficient API to work with)
• No need to make ourselves undesirable, once the RSS is consumed, Magnetissimo will wait 30 minutes before consuming it again. In practice we're not missing many torrents, if at all.
• One big disadvantage is that we're now lacking informations about the number of leechers and seeders of the torrents. This will have to be implemented in another PR, if the folks at EZTV don't fix their RSS. I'll try to contact them on that issue.