Added option remove_on_suspend

Previously the hosts entries where removed when the VMs are suspended, but
not added again when you called resume.
With this patch the hosts entries are only removed when you set the
remove_on_suspend option to true, and they are always added again when
you call resume.
Updated readme
Update README.md

Fixed code blocks
Merge pull request #4 from innogames/remove_on_suspend_option

Remove on suspend option