Docpie

* [change] use "Options" when parsing "Usage" and remove some `fix` method

Though it's not recommended, you can now write:


Usage: prog -iFILE

Options: -i FILE input file


It's not clear. You'd better write `-i<file>` instead.

* [new] notice user when a flag is not defined.('Unknown option: <option>')
* [fix] handle auto_handler before matching
* [new] `optionsfirst` argument
* [change] **break-change** remove `Docpie.option_text` attribute,
add `Docpie.option_sections`

* [fix] merging value bug. `Usage: prog [--repeat=<sth> --repeat=<sth>]`
matching `prog` will now give `'--repeat=[]'` instead of the old
wrong value `'--repeat=0'`

* [new] better error information notification.
* [fix] better `Either` handling. Now `Either` will be expanded and throwed
away. Which means now for


Usage: prog [-v | -vv | -vvv] cmd


can match `-v cmd`, `-vv cmd`, `-vvv cmd`. The old format also works


Usage: prog [-vvv | -vv | -v] cmd


but the new one is more readable.
* [fix] remove some old api, remove `save.py`

* [fix] `Docpie.tokens.Argv.auto_expand` handles `--` in a wrong way

* [new] Now `Docpie` can guess your long options. e.g. when you write both
`--verbose` & `--version`, then the `--verb` in argv will be interpreted
as `--verbose`, `--vers` as `--version`, the `--ver` will raise an error.