change website documentation

[andreamontanari]

Hi Tyler,

thank you for the amazing job with flexslider, but I found a little bug on the website
I was looking how to prevent keyboard navigation and on your website it's written that by using "keyboardNav" set as false you can disable it, while on your github documentation it's written "keyboard", I think it's a good solution to update the code online so people like me don't get lost anymore!

Cheers