#4153: update Unicode howto for Python 3.3

#4153: update Unicode howto for Python 3.3

* state that python3 source encoding is UTF-8, and give examples

* mention surrogateescape in the 'tips and tricks' section, and
  backslashreplace in the "Python's Unicode Support" section.

* Describe Unicode support provided by the re module.

* link to Nick Coghlan's and Ned Batchelder's notes/presentations.

* default filesystem encoding is now UTF-8, not ascii.

* Describe StreamRecoder class.

* update acks section

* remove usage of "I think", "I'm not going to", etc.

* various edits

* remove revision history and original outline