Carefully avoid using some characters in shell command
Carefully avoid using some characters in shell command

Close #171

dwrensha/vagrant-spk,sandstorm-io/vagrant-spk,ndarilek/vagrant-spk,ndarilek/vagrant-spk,ndarilek/vagrant-spk,sandstorm-io/vagrant-spk,dwrensha/vagrant-spk,sandstorm-io/vagrant-spk,dwrensha/vagrant-spk