Adds really basic akismet checking.  You need an API key from akismet in your config file

Look in config.ini.dist for an example of the config settings.  We will need to
add the setting on live (Lorna has an API key to use) when this feature goes live.
Any and all testing and feedback very VERY welcome!
It seems that [RFC 7239](http://tools.ietf.org/html/rfc7239) is close to what we want.

This defines the  `Forwarded` header which allows for passing originating IP address and host information through a proxy and also allows for extension tokens for other information.

We could check `Forwarded` for the 'for' and 'user-agent' tokens, so I could imagine that something like this would be acceptable:

    Forwarded: for=192.168.0.1;user-agent="Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/37.0.2049.0 Safari/537.36"

Note that there's also a de-facto header of `X-Forwarded-For` which is in use by various proxies today, but only handles IP address. RFC 7239 is intended to replace this with something more flexible.