Adding csv suppport to maxreport.

Example:

```bash
$ maxreport popular --csv --top 5
Running popular files report.

hits,file
8062,/bootstrap/master.css
4239,/bootstrap/favicon.ico
4016,/bootstrap/images/simple_icons/Facebook.png
4011,/bootstrap/images/simple_icons/Google.png
4010,/bootstrap/images/simple_icons/Twitter.png
```


```bash
$ maxreport stats --csv
Running summary stats report.

total hits,cache hits,non-cache hits,size
34540,27203,7337,65310302
```