Add synced .gopath

[phungleson]

When I go get inside VM, all the dependencies are in /opt/gopath of the guest VM however my text editor/shell is in the host. Therefore, it is kind of hard to take a look at the dependencies' src when necessary.

Suggested solution:

1. Create an empty folder .gopath in the repo
2. Synced that folder to the VM config.vm.synced_folder ".gopath/", "/opt/gopath"

Whenever we build in the VM we will have all the dependencies' src available in the host as well. Let me know if you have any other solution, I can make a PR for this.

[armon]

You can always just fetch the dependencies on your host using "go get -u ./...". Not sure we want to sync the dependencies using Vagrant, since it'll be much slower than doing on the host, and defeats the self-containment of the VM.