Package "build-essential" is installed on Travis.

o According to Build History "build-essential is
  already installed on Travis CI Boxes, therefore
  remove it from ".travis.yml".
Merge pull request #32 from h5b/post_controller

Unbreaking Rake Tests "post_test" and "post_controller_test" sounds right. But we need a real fix :/
Merge branch 'master' into graveio-box