Add check and reporting to apache_mod_cgi_bash_env

And some additional improvements.
Actually, my bad. Since you're using the scanner mixin, you should declare your check method as the following

```ruby
def check_host(ip)
```

Mentioned in the wiki I wrote:
https://github.com/rapid7/metasploit-framework/wiki/How-to-write-a-check%28%29-method