Remove leading underscores from internals
Simplify ArgconsumerType
Code cosmetics (lots of it)

also, fix regression in add_arg_group
No longer necessary to export ArgParseField
Small fix for "--" parsing
Examples code cosmetics
Remove leftorver debug code
Parsing code simplification

Use producer/consumer model to disentangle logic
Simplify/rationalize some function signatures
Add ParserState; clean up parsing code
Update number_regex
Cosmetics
Fix nargs (change Char->Symbol)
Fix show(::ArgConsumerType)
More cosmetics
Add keyword arguments to ArgParseSettings

updated docs, examples, tests
Add show(::ArgParseSettings)
Do not show String type in auto-help
Fix looks_like_an_option
Fixed issue with truncated shopts

also show settings default group
Merge branch 'cleanup'