WiP: fix environs tests on windows

Unfortunately, permission checking on Windows does not work as expected. For example, doing a:

```go
os.Chmod("C:/test.txt", 0600)
```

will set permissions to:

```
-rw-rw-rw-
```
Ah, I missed that you had escaped it on Windows. Use `regexp.QuoteMeta(os.PathSeparator)` then.