Update for 4.0 Compatability

Based this off of the sample here, http://www.advancedcustomfields.com/docs/tutorials/creating-a-new-field-type/, and just updated it to work.

There's still some old functions that seem to work. Not sure if they went away between ACF 3.x and 4.0, or if they were functions you called. I just did barebones to get it working.

Let me know what you think.