Adding a utility method for adding host entries

As much as this is a infrastructure-smell in the linux world, adding
hosts entries is still all to common in the windows world. This method
allows host entries to be configured to meet that need.

It can also be used when developing with vagrant to make sure that the
master and agent vms can see each other properly.
Merge branch 'master' into host_entry_method
switching method to use powershell wrapper
removing unused powershell command
renaming method to add_system32_hosts_entry
(gh-472) refactoring method so that is only supports windows and will raise error on other platforms
Merge branch 'master' into host_entry_method
fixing tests for add_system32_hosts_entry method
Merge pull request #420 from liamjbennett/host_entry_method

Adding a utility method for adding host entries