Update existing events to use new sponsor format

[mattstratton]

We have determined it is best to do the shared sponsors on a per-year basis (to help with sponsor logos changing over time). We need a volunteer to go through the existing /data/events folder and update all the sponsors to be named accordingly. Additionally, the existing /data/sponsors files need to be renamed to match these names, and the /static/img/sponsors directory files need to be renamed.

It is up to the person volunteering to do this to decided between 2016-chef or chef-2016 as the standard; just pick one, and whatever you decide, update the README as well (currently the README says to use chef-2016).

[mattstratton]

No longer needed. We will eventually handle this in the future with #125 but it's not needed in 2016.

[mattstratton]

This depends on #133, just for reference.