Release 0.4.0

Backwards-incompatible changes

• The Vagrant plugin vagrant-libcloud-helper is now required for attaching storage volumes to nodes.
• Virtualbox shared folders are disabled, in order to make Vagrant boxes resemble more closely nodes created by other providers.

Backwards-compatible changes

• Storage volumes can be hot-plugged (if the host operating system supports it).
• Vagrant node instances have an extension attribute called ex_ssh_client, a context manager wrapping an instance of libcloud.compute.ssh.SSHClient.
• The Vagrant plugin vagrant-proxyconf, if available in the host system, is set up in order to allow node deployments behind an HTTP proxy.