feat(README): add information about removing old box files

based on feedback from @cap10morgan in irc add details on removing old
box files.
Merge pull request #31 from philips/add-box-remove-instructions

feat(README): add information about removing old box files
Add vmware to virtualbox Vagrantfile
Merge pull request #32 from bfirsh/single-vmware-fusion-vagrantfile

Add vmware to virtualbox Vagrantfile
vbguest error workaround.
Merge pull request #34 from tsuyoshicho/vbguest-workaround

vbguest error workaround.
Clarify NFS password source.
Easy-to-uncomment instructions for NFS mounting

Special help for special people.
Merge pull request #39 from drnic/nfs-help

Easy-to-uncomment instructions for NFS mounting
fix(plugin): monkey-patch coreos plugin

Override the behavior of the upstream coreos guest
plugin to make it work with usr images.
doc(README): drop alt-setup
feat(provision): Add coreos-cloudinit provisioner
Merge pull request #45 from bcwaldon/fix-usr

Override upstream plugin; Add cloudinit provisioner
doc(README): Adjust to new command syntax for vagrant box remove
Merge pull request #48 from gmacario/fix-boxremove

doc(README): Adjust to new command syntax for vagrant box remove
fix(clustering): Use same codepath for single- and multi-node
Merge pull request #47 from bcwaldon/fix-usr

Implement clustering with coreos-cloudinit
fix(Vagrantfile): use amd64-usr for vmware
Merge pull request #54 from philips/usr-image-vmware

fix(Vagrantfile): use amd64-usr for vmware
refactor(plugin): Use cloud-config to provision networks and hostname