Fix Go tests on Windows

A couple of Go tests failure on Windows, fix code or tests to make them green:

--- FAIL: TestSaveAlwaysReportOption (0.15 seconds)
panic: remove C:\Users\IEUser\AppData\Local\Temp\test-repo999546479\test.git: Th
e process cannot access the file because it is being used by another process. [r
ecovered]
        panic: remove C:\Users\IEUser\AppData\Local\Temp\test-repo999546479\test
.git: The process cannot access the file because it is being used by another pro
cess.

--- FAIL: TestRunnerCallCommands (0.00 seconds)
        assert.go:15: V:/src/github.com/github/hub/commands/runner_test.go:42
        assert.go:24: ! 0 != 1

--- FAIL: TestEditor_openAndEdit_deleteFileWhenOpeningEditorFails (0.00 seconds)
        assert.go:15: V:/src/github.com/github/hub/github/editor_test.go:34
        assert.go:36: !  Failure

--- FAIL: TestGitHubRepo_OriginRemote (0.16 seconds)
        assert.go:15: V:/src/github.com/github/hub/github/localrepo_test.go:18
        assert.go:24: ! "V:\\src\\github.com\\github\\hub\\fixtures\\test.git" !
= "ssh://V/%5Csrc%5Cgithub.com%5Cgithub%5Chub%5Cfixtures%5Ctest.git"
Merge pull request #694 from github/windows_go_test_fix

Fix Go tests on Windows