Yaargh

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Backwards incompatible changes:

- Wrapped exceptions now cause ``dispatching.dispatch()`` to raise ``SystemExit(1)``
instead of returning without error. For most users, this means failed commands
will now exit with a failure status instead of a success.

Enhancements:

- Added support for Python 3.6, 3.7 and 3.8
- When using `skip_unknown_args=True`, not only does this now work as intended
(see bugfixes below) but in addition it stashes the unknown args in ``namespace._unknown_args``,
where they can be accessed by functions annotated with ``expects_obj``.
- Can control exit status (see Backwards Incompatible Changes above) when raising ``CommandError``
using the ``code`` keyword arg.

Fixed bugs:

- ``str`` annotations on ``*args`` would not result in the string being set as the help message,
as intended and as was already the case for normal args (PR 3).
- The `skip_unknown_args` option was broken and would always error

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Forked from argh, renamed to yaargh

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Backward incompatible changes:

- Dropped support for Python 2.6.

Enhancements:

- Added support for Python 3.5.
- Support introspection of function signature behind the `wraps` decorator
(issue 111).

Fixed bugs:

- When command function signature contained ``**kwargs`` *and* positionals
without defaults and with underscores in their names, a weird behaviour could
be observed (issue 104).

Other changes:

- Include the license files in manifest (PR 112).

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- Removed official support for Python 3.4, added for 3.5.
- Various tox-related improvements for development.
- Improved documentation.

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Fixed bugs:

- The undocumented (and untested) argument `dispatch(..., pre_call=x)`
was broken; fixing because at least one important app depends on it
(issue 63).

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This release is intended to be the last one before 1.0. Therefore a major
cleanup was done. This **breaks backward compatibility**. If your code is
really outdated, please read this list carefully and grep your code.

- Removed decorator `alias` (deprecated since v.0.19).

- Removed decorator `plain_signature` (deprecated since v.0.20).

- Dropped support for old-style functions that implicitly expected namespace
objects (deprecated since v.0.21). The `expects_obj` decorator is now
mandatory for such functions.

- Removed decorator `command` (deprecated since v.0.21).

- The `wrap_errors` decorator now strictly requires that the error classes
are given as a list (old behaviour was deprecated since v.0.22).

- The `allow_warnings` argument is removed from
`argh.completion.autocomplete()`. Debug-level logging is used instead.
(The warnings were deprecated since v.0.25).

Some more stuff has been scheduled **to be purged before 1.0**:

- Deprecated arguments `title`, `help` and `description` in `add_commands()`
helper function. See documentation and issue 60.

Other changes:

- Improved representation of default values in the help.

- Dispatcher can be configured to skip unknown arguments (issue 57).

- Added `add_subcommands()` helper function (a convenience wrapper
for `add_commands()`).

- `EntryPoint` now stores kwargs for the parser.

- Added support for default command *with* nested commands (issue 78).

This only works with Python 3.4+ due to incorrect behaviour or earlier
versions of Argparse (including the stand-alone one as of 1.2.1).

Due to argparse peculiarities the function assignment technique relies
on a special `ArghNamespace` object. It is used by default in `ArghParser`
and the shortcuts, but if you call the vanilla `ArgumentParser.parse_args()`
method, you now *have* to supply the proper namespace object.

Fixed bugs:

- Help formatter was broken for arguments with empty strings as default values
(issue 76).