Sh

- Removed old undocumented cruft of ARG1..ARGN and ARGV.
- Bugfix where `logging_enabled` could not be set from the importing module.
- Disabled garbage collection before fork to prevent garbage collection in child process.
- Major bugfix where cyclical references were preventing process objects (and their associated stdout/stderr buffers) from being garbage collected.
- Bugfix in RunningCommand and OProc loggers, which could get really huge if a command was called that had a large number of arguments.

- Changing status from alpha to beta.
- Python 3.3 officially supported.
- Documentation fix. The section on exceptions now references the fact that signals do not raise an exception, even for signals that might seem like they should, e.g. segfault.
- Bugfix with Python 3.3 where importing commands from the sh namespace resulted in an error related to `__path__`
- Long-form and short-form options to commands may now be given False to disable the option from being passed into the command. This is useful to pass in a boolean flag that you flip to either True or False to enable or disable some functionality at runtime.

- Making `Command` class resolve the `path` parameter with `which` by default instead of expecting it to be resolved before it is passed in. This change shouldn't affect backwards compatibility.
- Fixing a bug when an exception is raised from a program, and the error output has non-ascii text. This didn't work in Python < 3.0, because .decode()'s default encoding is typically ascii.