Add check for CF-Connecting-IP header in get_ipaddress

CF-Connecting-IP is set by clouflare to the connecting client's IP address. By prioritizing this header over other headers, it is more difficult for a client to spoof their ip and vote multiple times.
https://support.cloudflare.com/hc/en-us/articles/200170986-How-does-Cloudflare-handle-HTTP-Request-headers-

Converted bool to int to fix bug #92.

update wp_polls_update_poll to use current poll id

Add ternary operator so comparison works as expected

Update wp-polls.php

Allow filtering of the poll results markup.

Fix percentage calculation error