Add GCP Compute Engine & Kubernetes Integration

[EmersonDove]

This PR adds full support for GCP and Kubernetes.

GCP Usage:

machine1 = fogros2.GCPCloudInstance(
        project_id='gcp-project'
    )

Kubernetes Usage

machine1 = fogros2.GCPKubeInstance()

Requires gcloud CLI and/or kubectl on local host

Changes to review:

• The cloud instance exposes an ip property and now a vpn_ip property. Kubernetes has separate addresses for the two services so a modification was also made to the VPN class
• Enforced the ubuntu username in ClouldInstance

Known Issues:

• boto3 (any python dependencies) is not recognized on remote launch for both kube and GCP
• Depending on kubectl gcloud configuration a warning can disrupt the parsing done for kubernetes responses