vagrantfile: Automatically set up proper settings.
install: Set up Dockerfile syntax highlighting for vim.

I think there's still a problem so I'll have to investigate.
install: Report error messages when they happen.
vimrc: Prevent auto-wrapping lines in Dockerfiles.
Merge branch 'ps.add_vagrant_and_docker_helpers'

This branch adds a bunch of customizations I've been wanting for a while
now. It should be a lot more pleasant to work with Dockerfiles and
Vagrantfiles.