Update rakismet branch to recent enki (on Rails 3) 

I've freshened this branch to work with the current enki on Rails 3 and with Rakismet 1.3.0.  I've also added some specs to make sure the spam checking actually happens.  There are lots of commits from enki core, but only a few actual rakismet changes:

```
$ git log --oneline rakismet ^tapajos/rakismet ^xaviershay/master
d9ed618 Exclude spam comments from CommentActivity query
4857a90 Make akismet and rspec configs work for Ruby 2.0
5bbf4fe Benchmark and log rakismet spam? call
c28f6e1 Call rakismet's "spam?" method and train it with corrections
903d89e Update rakismet comment spam filtering to work on Rails 3
2dfeaa1 Merge branch 'master' into rakismet
```