Port WinRM Changes from go-winrm for inclusion in a WinRM Communicator for Packer

As per Packer issue https://github.com/mitchellh/packer/issues/451, this PR includes:

* Port of @sneal's WinRM changes from https://github.com/sneal/go-winrm (excluding wide-spread breakage introduced in 59fb19b77c698e3497813ffc7b879e245b3a5c06. This may need to be included down the track)
* CI setup using Travis-CI with Coveralls support (will need a new encrypted token when transferred across repos)
* Updated go-check library
* A local Vagrant setup to test winrm CLI locally

cc: @dylanmei @sneal