Added patch to build.sh to fix missing go-vnc, updated README

[dongyuzheng]

• Added patch to build.sh to fix missing go-vnc
• Updated README
  • Changing Golang version dependency to >= 1.6; < 2.0 because packer asks for 1.6 and Golang 1 has a compatibility promise
  • Fixed cannot find package "github.com/xenserver/packer-builder-xenserver/builder/xenserver/iso" in any of: #45

[dongyuzheng]

@rdobson , are there any problems with my PR?

[rdobson]

I'm not sure why this is required? the repo should be able to be vendored like the rest. Did you try this?

[dongyuzheng]

Yes, I followed exactly:

1. https://github.com/mitchellh/packer/blob/master/CONTRIBUTING.md#setting-up-go-to-work-on-packer
2. https://github.com/xenserver/packer-builder-xenserver/blob/master/README.md#compile-the-plugin

Perhaps I should change this to something like go get go-vnc, but either way, go-vnc is never downloaded in either process. It's happened to both me and another guy: #45

ASIDE:
I've been working with packer-builder-xenserver for Windows and I've noticed the following problems:

1. WinRM timeout is defaulted to 0s (expecting 20 minutes) WinRM timeout defaults to zero #52
2. ssh_username is still required (should be winrm_username)
3. plugin does not correctly get winrm host ip WinRM communicator uses wrong host and port #53
4. plugin does not correctly set winrm port, and specifying winrm_port in the config is ignored WinRM communicator uses wrong host and port #53

I've made some patches for 3 and 4 to make it work in the meanwhile, but please take a look. I didn't make a PR because they're too hackish.