Merge branch 'release/0.3.0-alpha.3' into develop
Fix host-only interface automatic creation. Fixes #58.
Prevent VMs from starting if host doesn't support guest OS.

If the Guest is a 64bit os but the host's CPU doesn't provide the
hardware virtualization extensions necessary for running virtualized
64bit OS, prevent the VM from starting. Fixes #60.
Add diagnostics function in vmfest/manager.

(manager/diagnostics my-server) will return a map with relevant
information about the state and configuration of the host and vmfest
models and machines.
Allow late addition of vbox library in the classpath.
Release 0.3.0-alpha.4
Merge branch 'release/0.3.0-alpha.4'