dev: install bundle as part of setup
dev: travis-ci

* .travis.yml: created using info from
  [[https://groups.google.com/forum/#!msg/travis-ci/l8DIsdRt5P4/BIPmkvIepegJ][here]]
  and [[https://github.com/shoes/shoes/blob/develop/.travis.yml][here]]
bugfix: travis-ci: aptitude -> apt-get
bugfix: travis: limit ghc heap size
dev: separate build into build and doc stages
travis: don't build doc
travis: use Makefile to install dependencies
bugfix: travis: add cabal-src as a dependency
dev: refactor sources.txt
dev: refactor Makefile

blog/sources.txt (for cabal-meta) no longer pulls in dependencies. i'm
not really sure how i'll end up using cabal-meta. ideally i should be
using it as a drop-in replacement for 'cabal install'. but what about
'cabal build'? i think it's best to use cabal-meta for ensuring the
dependencies are installed, and the Makefile uses it internally