Argopt

- allow `ARG` format (5)
- remove `argparse` dependency for `py>=2.7` (6)
- add unit tests
- fix CI py26 tests

- support `epilog`ue
- ignore section titles (usage|options|arguments): when not at start-of-line
- update documentation and CI tests

- warn about duplicate options
- epilog support (2)
- exposed default `formatter_class=argparse.RawDescriptionHelpFormatter`
- py26 `argparse` dependency
- exposed default `logLevel=logging.NOTSET`

- added python 2.6 support
- update examples and documentation
- add tests (py3.6, pypy3)
- exposed `DictAttrWrap`

- default positional arguments [feature]
- `-v` and `--version` conflict resolution [feature]
- update documentation
- update examples
- coverage, tests and misc tidying