[subset] Fix example

Fixes https://github.com/behdad/fonttools/issues/192
Add back fontTools.xmlWriter

Fixes https://github.com/behdad/fonttools/issues/190
Revert "Add back fontTools.xmlWriter"

This reverts commit f8c35b6f98717a3f1f799b722e3bcd5b9303735c.
Res is not available in Python 3
Merge pull request #196 from moyogo/py3mac

Res is not available in Python 3