Wordpress Scanner

This PR adds a Wordpress Scanner to find Wordpress versions on the network.
This should replace PR #2621 from @0pc0deFR

Wasn't sure which report info should be used. I wanted to use the report_web_site, but it looks like there is no option for a path. Maybe you have some feedback on this.

Output from this module:
```
msf auxiliary(wordpress_scanner) > run
[*] Trying ip 192.168.18.127
[-] 192.168.18.127:80 - Error connecting to /wordpress/
[*] Scanned 1 of 4 hosts (025% complete)
[*] Trying ip 192.168.18.128
[-] 192.168.18.128:80 - Error connecting to /wordpress/
[*] Scanned 2 of 4 hosts (050% complete)
[*] Trying ip 192.168.18.129
[+] 192.168.18.129 running Wordpress 3.6.1
[*] Scanned 3 of 4 hosts (075% complete)
[*] Trying ip 192.168.18.130
[-] 192.168.18.130:80 - Error connecting to /wordpress/
[*] Scanned 4 of 4 hosts (100% complete)
[*] Auxiliary module execution completed
```