changed the spam/flood detection plugin and algorithm

The plugin now works for a single channel only. This simplified a lot.
If you need to run it in more than one channel, please implement
multi-plugins =)

Also changed the detection algorithm. Now takes into account line
length, and webchat status, as well as the number of repeated lines.
added __future__ imports to some files

Some files with unicode literals broke after the change back from python
3 because they contained non-ascii characters. Added future import for
unicode_literals for each file that declared an encoding.

Also fixed votd calculation by adding future import for division.