- Move all .travis/*.sh functionality directly into .travis.yml
- Install Alex/Happy from PPA instead of compiling them by hand
- Skip Shake progress indicators, as they're rather useless
  on clean-slate Travis builds, and clutter up the log
- Don't use a Cabal sandbox for building so Travis can share
  $HOME/.cabal
- boot/configure only after the Shake build system is in place,
  otherwise some required *.in files are not converted, and
  Shake fails