Add detail screen

This actually isn't "finished", but I think it's worthwhile to get it
into master before working on the individual problems. I've created
issues for all of the known issues, but basically:

- [x] Properties from `TBEmployee` are implicitly unwrapped optionals. This
  can cause crashes if an employee doesn't have this info in their
  profile and we try to access it. Specifically, this is a problem for
  start dates and personal website urls.
- [ ] We're still showing cells even if the employee doesn't have
  information to use in that cell
- [x] We're being horribly inefficient with our use of `NSDateFormatter` in
  the employee view model. We should fix that.
yes you could ... by then fmap / apply would check for the existence of the tuple which would always be there .. just the values inside could be .None ... in which case the function you are applying with would need to take 2 optional values ... so it wouldn't work in this scenario but yes you can use tuples as argument lists for functions.