Handle incompatibility for Vagrant 1.3.0

In Vagrant 1.3.0, `config.ssh.max_tries` is gone and `config.ssh.timeout` has been replaced by `config.vm.boot_timeout`

I updated the Vagrantfile for compatibility with 1.3.0 and up.

[Vagrant Changelog](https://github.com/mitchellh/vagrant/blob/master/CHANGELOG.md)