Enable travis-ci
Travis: Install racket to use tests
Travis: Install racket to use tests
Add travis badge
Travis: newer racket
Travis: add-apt-repositoru non-interactive

also: make Build image point to (not yet exisitng) travis-ci path for
@samth
Travis: try pypy
Merge branch 'master' into issue7-specific-cons

* master:
  Travis: try pypy
  Travis: add-apt-repositoru non-interactive
  Travis: newer racket
  Add travis badge
  Travis: Install racket to use tests
  Travis: Install racket to use tests
  Enable travis-ci