Added %d as an extended replacement for directory name

[jtuskan]

This is my first pull request. Hopefully, everything is in line. This change would allow the use of the file's directory name in replacements. It would be helpful for multi-entry applications.

// Replacement based on the file being processed
// Stream contains ['\root\views\map\index.js', '\root\views\home\index.js']
htmlreplace({
  js: {
    src: null,
    tpl: '<script src="%d.%f.bundle.js"></script>'
  }
})
// Outputs: <script src="map.index.bundle.js"></script>, <script src="home.index.bundle.js"></script>

Please let me know if I can improve my request.
Best regards,
Joe

[coveralls]

Coverage decreased (-0.6%) to 97.484% when pulling 00b7a9e on jtuskan:master into 38e66fd on VFK:master.