Add Vagrantfile, document how to run test suite in a vagrant VM

Vagrantfile

@@ -0,0 +1,20 @@
+# -*- mode: ruby -*-
+# vi: set ft=ruby :
+
+Vagrant.configure(2) do |config|
+  config.vm.box = "bento/ubuntu-16.04"
+
+  config.vm.synced_folder ".", "/go/src/github.com/containernetworking/cni"
+
+  config.vm.provision "shell", inline: <<-SHELL
+    set -e -x -u
+
+    apt-get update -y || (sleep 40 && apt-get update -y)
+    apt-get install -y golang git
+    echo "export GOPATH=/go" >> /root/.bashrc
+    export GOPATH=/go
+    go get github.com/tools/godep
+    cd /go/src/github.com/containernetworking/cni
+    /go/bin/godep restore
+  SHELL
+end