Rolling CSV's

Here you can find some changes into Metrics.Net that enables me to create a rolling CSV file reporter(by using Log4Net RollingFileAppender). The issue with existing csv reporter is that we plan to use it in production and the files will grow in size. I had to extract some interfaces in Metrics.Net in order to make it possible.

I am new to git and github, therefore can you review if the code in this pull request matches the expectation of the project?

Would you be able to host Metrics.RollingCsvReporter in the nuget as another library (like Nancy)?
I can host it myself, but in order to do that I need to have the some changes in core Metrics.Net (like MetricsReports class (see commit)).