Update docstrings based on existence of Python 3.3.3
Clean up, add some missing pieces, document a lot

For the purpose of documentation, and also because it's generally
useful, this adds the `explain_unicode` function, which prints the name
and codepoint of each character in a Unicode string.

It also adds aliases such as 'sloppy-cp1252' for 'sloppy-windows-1252',
and adds the 'sloppy-cp854' codec.
Merge branch 'codecs' of github.com:LuminosoInsight/python-ftfy into codecs

Conflicts:
	tests/test_unicode.py
fix a doctest that broke on Python 3