`.\share\git-tfs\extract-git-tfs-path.ps1 .\GitTfs-0.16.0.zip` wasn't working

If I didn't pass an argument, the `test-path` call failed because
of an empty argument.

Opening the zip file with `shell.namespace` was failing because
the path was a relative path.

This change fixes both of those problems.
Update to git-tfs 0.16.0
Update to 0.16.1.
Merge pull request #11 from github/git-tfs-0.16

Update to git-tfs 0.16.0