Add copyright header for Tom Willemse; bump year

Tom (@ryuslash) is responsible for inspiring me to continue development
on DisPass at a time where I was slacking very much. He has brought
great ideas to the project and continues to do so. In spite of my
continous slacking ways Tom actually writes new code and has created
awesome other DisPass stuff like:

- an Emacs interface for DisPass (https://github.com/ryuslash/dispass.el)
- a conkeror interface for DisPass (https://github.com/ryuslash/cdispass)
- the DisPass algorithms implemented in C
  (https://github.com/ryuslash/libdispass)

Therefore sharing the copyright is well deserved and very fair.