Add cookbook for skipfish

PT #45996869

Adds support for installing and configuring skipfish via chef.

Verification Steps:

- [ ] Clone Ubuntu 64-bit VM
- [ ] Run chef bootstrap.sh and clone Chef repo as described in the [README](https://github.com/rapid7/Chef-Metasploit/blob/master/README.md#step-1)
- [ ] sudo chef-solo -j /var/chef/solo-nodes/skipfish.json
- [ ] Try scanning the web target VM:
        
          /opt/skipfish-2.10b/skipfish -o ~/skipfish -W- -L http://10.6.201.161/
    
    You can `Ctrl+C` after verifying the scanner works.