FEATURE: export screened IPs list in a CSV file

Example:

![screen shot 2014-11-21 at 11 34 09 pm](https://cloud.githubusercontent.com/assets/5732281/5147555/47c5a5dc-71dc-11e4-822b-d6855a4ea4b1.png)

Example CSV file:

![screen shot 2014-11-22 at 12 05 32 am](https://cloud.githubusercontent.com/assets/5732281/5147556/4fda3c38-71dc-11e4-8519-2e8c2367d923.png)

cc @eviltrout @coding-horror