Add ability to port-forward TCP docker service to host machine

Vagrantfile will check if $expose_docker_tcp is set in config.rb, and
will forwad the docker port (tcp/4243) to the specified port on the host.

Service for docker to listen on port 4243 added to user-data.
Merge pull request #100 from mattbailey/master

Add ability to port-forward TCP docker service to host machine
chore(*): add warning about serial logging performance
Merge pull request #109 from jonboulle/master

chore(*): add warning about serial logging performance
fix(README): bump the required version numbers

Based on feedback on the mailing list recommend vagrant 1.6 and virtualbox 4.3.10
feat(Vagrantfile): alter configuration to allow use as Docker host vm

turning off guest additions and vboxsf makes this possible, which is taken directly from the default docker host configuration: https://github.com/mitchellh/vagrant/blob/master/plugins/providers/docker/hostmachine/Vagrantfile
feat(channel): Allow user to configure CoreOS update channel
Merge pull request #102 from bcwaldon/configurable-channel

feat(channel): Allow user to configure CoreOS update channel
if exposing docker api locally use a unique port for each box in the cluster
Merge pull request #104 from ddollar/unique-port-forward

if exposing docker api locally use a unique port for each box in the cluster
Merge pull request #115 from shopkeep/allow-docker-host-vm

feat(Vagrantfile): alter configuration to allow use as Docker host vm
Fix up a couple of tyops.
Trivial indent, space v. tabs
Merge pull request #119 from thorduri/minor

Minor fix ups.
alpha is a string, and needs quoting
Merge pull request #120 from spkane/fix-config

alpha is a string, and needs quoting
Add vmware fusion GUI support
Merge pull request #122 from spkane/fusion-gui

Add vmware fusion GUI support
Convert to the official IANA port for Docker
Use full paths to config.rb and user-data to better support docker provider