`aws.associate_public_ip = true` should be performed when user used default_vpc.  Key should not be symbol but string.
`aws.associate_public_ip = true` should be performed when user used default_vpc.  Key should not be symbol but string.

related to #33.

fonhorst/vagrant-mesos,hippolin/vagrant-mesos,mesosphere/vagrant-mesos,dchesterman/vagrant-mesos,cgvarela/vagrant-mesos,yoeluk/vagrant-mesos,emccode/vagrant,everpeace/vagrant-mesos,mesosphere/vagrant-mesos,jonasrosland/vagrant-mesos,prasincs/vagrant-mesos,hippolin/vagrant-mesos,yoeluk/vagrant-mesos,emccode/vagrant,afrantisak/vagrant-mesos,yoeluk/vagrant-mesos,codedellemc/vagrant,fonhorst/vagrant-mesos,cgvarela/vagrant-mesos,dchesterman/vagrant-mesos,scorpionis/vagrant-mesos,scorpionis/vagrant-mesos,scorpionis/vagrant-mesos,prasincs/vagrant-mesos,codedellemc/vagrant,everpeace/vagrant-mesos,afrantisak/vagrant-mesos,mesosphere/vagrant-mesos,jonasrosland/vagrant-mesos,emccode/vagrant,dchesterman/vagrant-mesos,cgvarela/vagrant-mesos,afrantisak/vagrant-mesos,hippolin/vagrant-mesos,codedellemc/vagrant,prasincs/vagrant-mesos,everpeace/vagrant-mesos,fonhorst/vagrant-mesos,jonasrosland/vagrant-mesos