Always log request body for POST and PUT methods

I tried HttpLogger with [Faraday](https://github.com/lostisland/faraday) using the Net::HTTP adapter. I noticed that the request body for POST and PUT requests were not being logged.

It turns out that Faraday uses the Net::HTTPGenericRequest class for all requests. (See https://github.com/lostisland/faraday/blob/master/lib/faraday/adapter/net_http.rb#L55).

This pull request makes sure the request body gets logged regardless of the specific class of the request object. For consistency, I also renamed the method from ```log_post_put_params``` to ```log_request_body```.