Made read_forwarded_ports error handling generic

This also future proofs the plugin should the VMWare providers start supporting that method.
Ensure the chef task running file doesn't exist from a previous failure
Refactored monkey patch directory layout

Vagrant monkey patches folder structure now matches that of vagrant 1.2 release. Also removed global helper require form plugin.rb.
Add powershell note to readme
Merge pull request #78 from cleblanc87/master

Add powershell note to readme
Doc: Add instructions for source install

This should help cut down on folks asking how to 
install from source.

This also includes a gist that I worked through 
with another person that was trying to get this
installed.
Merge pull request #81 from ferventcoder/doc/add-install-prerelease

Doc: Add instructions for source install
Merge branch 'vagrant-1.2' of github.com:WinRb/vagrant-windows into vagrant-1.2

Conflicts:
	lib/vagrant-windows/communication/winrmcommunicator.rb
Merge remote-tracking branch 'origin/master' into vagrant-1.2

Conflicts:
	README.md