csv23: Python 2/3 Unicode CSV Compatibility Layer

csv23 provides the unicode-based API of the Python 3 `csv` module for Python 2 and 3. It allows code to run under both versions of Python by abstracting the bytes vs. text differences and adhering to the newer unicode-based interface. The library defaults to UTF-8 encoding and addresses several known bugs in the standard library's `csv` module. The current version is 0.3.4, and it is primarily in maintenance mode for cross-Python 2/3 compatibility features.