first iteration of more friendly UI
Style the buttons for known 2015 candidates similarly
Show the option to add new candidates even if there are known candidates
Use the same ID if you're updating a person

Changing a person's full name created an error because the code would
generate a new ID and then there would be a mismatch between the ID
being PUT to and the ID in the updated data. Instead, only include an ID
if we're creating a new person.
When creating a person, try a new slug if the ID already exists
Merge branch 'ui-design'