Add options for server creation

Fix #25
Fix #78
Fix #82
Fix #83
Merge pull request #99 from ggiamarchi/nova_opts

Add options for server creation
Release 0.3.3
Merge branch 'v0.3.x'
Add gem version badge
Deprecate ssh_username in provider config
use ssh.username and ssh.port standard options in the provider

Fix #88