import_posterous was broken and failing silently

Looks like it was only an issue when you assign a hostname, which you have to do when you have multiple blogs on your posterous account (it fails with an appropriate error message if you don't set a --posterous-host when multiple blogs are on the account).

From looking at code, I see site was never assigned when a hostname was set. Added assignment and I have now successfully imported my posterous blog.

I don't have any context for the time.sleep(2), I assume it's just to make sure request to posterous API don't hit a rate limit but I don't think it's really necessary at that early stage (immediately after new line). Left it in until I have more context.