move unittest helpers into a separate file
fix #35

Also add an option `direct-reply` to control the number of comments
on a thread without referencing a child (to avoid a simple while loop
that `curl -XPOST ...` the url).

Defaults to 3, that means a /24 (or /48 for IPv6) address can only post
3 direct responses on a thread at all.
add unittest for spam guard
add option reply-to-self, defaults to false
fix Python 3.3
Merge branch 'fix/spam-guard'