setAdmin
Sets the user's admin status.
viewmodel.setAdmin(user, isAdmin)
Sets the user's admin status.
Parameters
- 
			
user
{User}The user object that will be set or unset as an admin.
 - 
			
isAdmin
{Boolean}Whether the user should be set as an admin.
 
Returns
{Promise<User | } | The | save | promise | that | resolves | to | a>}
		@return {Promise<bitballs/models/user} The save promise that resolves to a user.