Add information about {ajax: false}

[Silex]

This is just a pull request to start thinking about updating the documentation about this. Maybe it's better if you update the doc as you know all the places where this should be documented, otherwise tell me the places and I'll add some commits.

[maccman]

Can you put this in http://spinejs.com/docs/ajax instead?

[Silex]

I'll recreate the pull request from the master branch instead