Get tests passing on Windows.

* Use Join() from "path/filepath" instead of "path" for OS-compatible
  paths.
* Use os.RemoveAll("name") instead of bash.run("rm -f name").
* Handle CRLF line endings in tail_test.go.
Remove no-longer-used bash() and run().
Bind to local 127.0.0.1 insted of 0.0.0.0.

This avoids errors from firewalls that block binding on external
interfaces.